Q.1 A clock hung on a wall has marks instead of numbers on its dial. On the opposite wall there is a mirror, and the image of the clock in the mirror if read, indicates the time as \(8: 20\). What is the time in the clock-

(1) \(3: 40\)

(2) \(4: 40\)

(3) \(5: 20\)

(4) \(4: 20\)

Q.2 A ray of light incident on a plane miror at an angle of incidence of \(30^{\circ}\). The deviation produced by the mirror is-

(1) \(30^{\circ}\)

\((2) 60^{\circ}\)

(3) \(90^{\circ}\)

(4) \(120^{\circ}\)

Q.3 The image of a real object formed by a plane mirror is-

(1) Erect, real and of equal size

(2) Erect, virtual and of equal size

(3) Inverted, real and of equal size

(4) Inverted, virtual and of equal size

Q.4 Two mirrors are inclined at an angle \(\theta\) as shown in the figure. Light ray is incident parallel to one of the mirrors. Light will start retracing its path after third reflection if:

(1) \(\theta=45^{\circ}\)

(2) \(\theta=30^{\circ}\)

(3) \(\theta=60^{\circ}\)

(4) all three

Q.5 If an object is placed symmetrically between two plane mirrors, inclined at an angle of \(72^{\circ}\), then the total number of images formed is-

(1) 5

(2) 4

(3) 2

(4) Infinite

Q.6 A man \(180 \mathrm{~cm}\) high stands in front of a plane mirror. His eyes are at a height of \(170 \mathrm{~cm}\) from the floor. Then the minimum length of plane mirror for him to see his full length image is-

(1) \(90 \mathrm{~cm}\)

(2) \(180 \mathrm{~cm}\)

(3) \(45 \mathrm{~cm}\)

(4) \(360 \mathrm{~cm}\)

Q.7 Two vertical plane mirrors are inclined at an angle of \(60^{\circ}\) with each other.A Aray of light travelling horizontally is reflected first from one mirror and then from the other. The resultant deviation is

(1) \(60^{\circ}\)

(2) \(100^{\circ}\)

(3) \(180^{\circ}\)

(4) \(240^{\circ}\)

Q.8 An object is at a distance of \(0.5 \mathrm{~m}\) in front of a plane mirror. Distance between the object and image is

(1) \(0.5 \mathrm{~m}\)

(2) \(1 \mathrm{~m}\)

(3) \(0.25 \mathrm{~m}\)

(4) \(1.5 \mathrm{~m}\)

Q.9 A convex mirror has a focal length \(\mathrm{f}\). Areal object is placed at a distance \(\mathrm{f}\) in front of it from the pole, then it produces an image at-

(1) Infinity

\((2) \mathrm{f}\)

(3) \(f / 2\)

(4) \(2 \mathrm{f}\)

Q.10 The largest distance of the image of a real object from a convex mirror of focal length \(10 \mathrm{~cm}\) can be-

(1) \(20 \mathrm{~cm}\)

(2) Infinite

(3) \(10 \mathrm{~cm}\)

(4) Depends on the position of the object

Q.11 Which of the following can form erect, virtual, diminished image?

(1) plane mirror

(2) concave mirror

(3) convex mirror

(4) none of these Q.12 A convex mirror of focal length \(\mathrm{f}\) forms an image which is \(1 / \mathrm{n}\) times the object. The distance of the object from the mirror is

(1) \((n-1) f\)

(2) \(\left(\frac{n-1}{n}\right) f\)

(3) \(\left(\frac{n+1}{n}\right) f\)

(4) \((n+1) f\)

Q.13 The field of view is maximum for

(1) Plane mirror

(2) Concave mirror

(3) Convex mirror

(4) Cylindrical mirror

Q.14 The focal length of a concave mirror is fand the distance from the object to the principle focus is \(\mathrm{x}\). The ratio of the size of the image to the size of the object is

(1) \(\frac{f+x}{f}\)

(2) \(\frac{f}{x}\)

(3) \(\sqrt{\frac{f}{x}}\)

(4) \(\frac{f^{2}}{x^{2}}\)

Q.15 Image formed by a convex mirror is

(1) Virtual

(2) Real

(3) Enlarged

(4) Inverted

Q.16 The image formed by a convex mirror of focal length \(30 \mathrm{~cm}\) is a quarter of the size of the object. The distance of the object from the mirror is

(1) \(30 \mathrm{~cm}\)

(2) \(90 \mathrm{~cm}\)

(3) \(120 \mathrm{~cm}\)

(4) \(60 \mathrm{~cm}\)

Q.17 Total internal reflection occurs in waves, when wave enters-

(1) Glass from air

(2) Air from vaccum

(3) Water from air

(4) Air from water

Q.18 Time taken to cross a \(4 \mathrm{~mm}\) window glass of refractive index 1.5 will be-

(1) \(2 \times 10^{-8} \mathrm{sec}\)

(2) \(2 \times 10^{8} \mathrm{sec}\)

(3) \(2 \times 10^{-11} \mathrm{sec}\)

(4) \(2 \times 10^{11} \mathrm{sec}\)

Q.19 A light wave travels from glass to water. The refractive index for glass and water are \(\frac{3}{2}\) and \(\frac{4}{3}\) respectively. The value of the critical angle will be:

(1) \(\sin ^{-1}\left(\frac{1}{2}\right)\)

(2) \(\sin ^{-1}\left(\frac{9}{8}\right)\)

(3) \(\sin ^{-1}\left(\frac{8}{9}\right)\)

(4) \(\sin ^{-1}\left(\frac{5}{7}\right)\)

Q.20 The wavelength of light in vacuum is \(6000 \AA\) and in a medium it is \(4000 \AA\). The refractive index of the medium is:

(1) 2.4

(2) 1.5

(3) 1.2

(4) 0.67

Q.21 A beam of light is converging towards a point. A plane parallel plate of glass of thickness t, refractive index \(\mu\) is introduced in the path of the beam. The convergent point is shifted by (assume near normal incidence):

(1) \(\mathrm{t}\left(1-\frac{1}{\mu}\right)\) away

(2) \(\mathrm{t}\left(1+\frac{1}{\mu}\right)\) away

(3) \(t\left(1-\frac{1}{\mu}\right)\) nearer

(4) \(\mathrm{t}\left(1+\frac{1}{\mu}\right)\) nearer

Q.22 When a beam of light goes from denser medium \(\left(\mu_{\mathrm{d}}\right)\) to rarer medium \(\left(\mu_{\mathrm{r}}\right)\), then it is generally observed that magnitude of angle of incidence is half that of angle of refraction. Then magnitude of incident angle will be- \(\left(\right.\) here \(\left.\mu=\mu_{\mathrm{d}} / \mu_{\mathrm{r}}\right)\)

(1) \(2 \sin ^{-1}\left(\frac{\mu}{2}\right)\)

(2) \(2 \cos ^{-1} \mu\)

(3) \(\cos ^{-1}\left(\frac{\mu}{2}\right)\)

(4) \(2 \cos ^{-1}\left(\frac{\mu}{2}\right)\)

Q.23 To an observer on the earth the stars appears to twinkle. This can be ascribed to

(1) The fact that stars do not emit light continuosly

(2) Frequent absorption of star light by their own atmosphere

(3) Frequent absorption of star light by the earth's atmosphere

(4) The refractive index fluctuations in the earth's atmosphere

Q.24 Refractive index for a material for infrared light is

(1) Equal to that of ultraviolet light

(2) Less than that for ultraviolet light

(3) Equal to that for red colour of light

(4) Greater than that for ultraviolet light

Q.25 If \(\mu_{\mathrm{i}} \mu_{\mathrm{j}}\) represents refractive index when a light ray goes from medium \(\mathrm{i}\) to medium \(\mathrm{j}\), then the product \({ }_{2} \mu_{1} \times{ }_{3} \mu_{2} \times{ }_{4} \mu_{3}\) is equal to

(1) \({ }_{3} \mu_{1}\)

\((2)_{3} \mu_{2}\)

(3) \(\frac{1}{{ }_{1} \mu_{4}}\)

(4) \({ }_{4} \mu_{2}\)

Q.26 The wavelength of light diminishes \(\mu\) times ( \(\mu=1.33\) for water) in a medium. Adriver from inside water looks at an object whose natural colour is green. He sees the object as

(1) Green

(2) Blue

(3) Yellow

(4) Red

Q.27 A diver in a swimming pool wants to signal his distress to a person lying on the edge of the pool by flashing his water proof flash light

(1) He must direct the beam vertically upwards

(2) He has to direct the beam horizontally

(3) He has to direct the beam at an angle to the vertical which is slightly less than the critical angle of incidence for total internal reflection

(4) He has to direct the beam at an angle to the vertical which is slightly more than the critical angle of incidence for the total internal reflection

Q.28 The wavelength of light in two liquids ' \(x\) ' and ' \(y\) ' is \(3500 \AA\) and \(7000 \AA\), then the critical angle of \(x\) relative to y will be

(1) \(60^{\circ}\)

(2) \(45^{\circ}\)

(3) \(30^{\circ}\)

(4) \(15^{\circ}\)

Q.29 Total internal reflection of a ray of light is possible when the \(\left(i_{c}=\right.\) critical angle, \(i=\) angle of incidence)

(1) Ray goes from denser medium to rarer medium and \(i<i_{c}\)

(2) Ray goes from denser medium to rarer medium and \(i>i_{c}\)

(3) Ray goes from rarer medium to denser medium and \(i>i_{c}\)

(4) Ray goes from rarer medium to denser medium and \(i<i_{c}\)

Q.30 The critical angle for diamond (refractive index \(=2\) ) is

(1) About \(20^{\circ}\)

(2) \(60^{\circ}\)

(3) \(45^{\circ}\)

(4) \(30^{\circ}\)

Q.31 The reason for shining of air bubble in water is

(1) Diffraction of light

(3) Scattering of light

(2) Dispersion of light

(4) Total internal reflection of light Q.32 With respect to air critical angle in a medium for light of red colour \(\left[\lambda_{1}\right]\) is \(\theta\). Other facts remaining same, critical angle for light of yellow colour \(\left[\lambda_{2}\right]\) will be

(1) \(\theta\)

(2) More than \(\theta\)

(3) Less than \(\theta\)

(4) \(\frac{\theta \lambda_{1}}{\lambda_{2}}\)

Q.33 'Mirage' is a phenomenon due to

(1) Reflection of light

(2) Refraction of light

(3) Total internal reflection of light

(4) Diffraction of light

Q.34 Given that velocity of light in quartz \(=1.5 \times 10^{8} \mathrm{~m} / \mathrm{s}\) and velocity of light in glycerine \(=(9 / 4) \times 10^{8} \mathrm{~m} / \mathrm{s}\). Now a slab made of quartz is placed in glycerine as shown. The shift of the object produced by slab is

(1) \(6 \mathrm{~cm}\)

(2) \(3.55 \mathrm{~cm}\)

(3) \(9 \mathrm{~cm}\)

(4) \(2 \mathrm{~cm}\)

Q.35 An object is placed at a distance of \(20 \mathrm{~cm}\), in rarer medium, from the pole of a convex spherical refracting surface of radius of curvature \(10 \mathrm{~cm}\). If the refrective index of the rarer medium is 1 and of the refracting medium is 2 , then the position of the image is at-

(1) \((40 / 3) \mathrm{cm}\) from the pole \& inside the denser medium

(2) \(40 \mathrm{~cm}\) from the pole \(\&\) inside the denser medium.

(3) \((40 / 3) \mathrm{cm}\) from the pole \& outside the denser medium

(4) \(40 \mathrm{~cm}\) from the pole \(\&\) outside the denser medium.

Q.36 There is a small black dot at the centre \(\mathrm{C}\) of a solid glass sphere of refractive index \(\mu\). When seen from outside, the dot will appear to be located:

(1) away from \(\mathrm{C}\) for all values of \(\mu\)

(2) at \(C\) for all values of \(\mu\)

(3) at \(\mathrm{C}\) for \(\mu=1.5\), but away from \(\mathrm{C}\) for \(\mu \neq 1.5\)

(4) at \(\mathrm{C}\) only for \(\sqrt{2} \leq \mu \leq 1.5\).

Q.37 The image for the converging beam after refraction through the curved surface is formed at:

(1) \(x=40 \mathrm{~cm}\)

(2) \(x=\frac{40}{3} \mathrm{~cm}\)

(3) \(x=-\frac{40}{3} \mathrm{~cm}\)

(4) \(x=\frac{180}{7} \mathrm{~cm}\) 

\section{GEOMETRICAL OPTICS}

Q.38 The refractive index of the material of prism of \(60^{\circ}\) angle is \(\sqrt{2}\). At what angle the ray of light be incident on it so that minimum deviation takes place?

(1) \(45^{\circ}\)

(2) \(60^{\circ}\)

(3) \(30^{\circ}\)

(4) \(75^{\circ}\)

Q.39 If the critical angle for the medium of prism is \(\mathrm{C}\) and the angle of prism is \(\mathrm{A}\), then there will be no emergent ray when -

(1) \(\mathrm{A}<2 \mathrm{C}\)

(2) \(A=2 C\)

(3) \(\mathrm{A}>2 \mathrm{C}\)

(4) \(A \geq 2 C\)

Q.40 A ray of monochromatic light is incident on one refracting face of a prism of angle \(75^{\circ}\). It passes through the prism and is incident on the other face at the critical angle. If the refractive index of the material of the prism is \(\sqrt{ } 2\), the angle of incidence on the first face of the prism is

(1) \(30^{0}\)

(2) \(45^{0}\)

(3) \(60^{0}\)

(4) \(0^{0}\)

Q.41 A ray of light is incident at angle \(i\) on a surface of a prism of small angle A and emerges normally from the opposite surface. If the refractive index of the material of the prism is \(\mu\), the angle of incidence \(i\) is nearly equal to :

(1) \(\mathrm{A} / \mu\)

(2) \(\mathrm{A} /(2 \mu)\)

(3) \(\mu \mathrm{A}\)

(4) \(\mu \mathrm{A} / 2\)

Q.42 A prism having an apex angle of \(4^{0}\) and refractive index of 1.50 is located in front of a vertical plane mirror as shown. A horizontal ray of light is incident on the prism. The total angle through which the ray is deviated is:

(1) \(4^{\circ}\) clockwise

(2) \(178^{\circ}\) clockwise

(3) \(2^{\circ}\) clockwise

(4) \(8^{\circ}\) clockwise

Q.43 A parallel beam of monochromatic light is incident at one surface of a equilateral prism. Angle of incidence is \(55^{\circ}\) and angle of emergence is \(46^{\circ}\). The angle of minimum deviation will be

(1) Less than \(41^{\circ}\)

(2) Equal to \(41^{\circ}\)

(3) More than \(41^{\circ}\)

(4) None of the above

Q.44 A biconvex lens with equal radii of curvature has refractive index 1.6 and focal length \(10 \mathrm{~cm}\). Its radius of curvature will be:

(1) \(20 \mathrm{~cm}\)

(2) \(16 \mathrm{~cm}\)

(3) \(10 \mathrm{~cm}\)

(4) \(12 \mathrm{~cm}\)

Q.45 A convex lens forms a real image \(9 \mathrm{~cm}\) long on a screen. Without altering the position of the object and the screen, the lens is displaced and we get again a real image \(4 \mathrm{~cm}\) long on the screen. Then the length of the object is-

(1) \(9 \mathrm{~cm}\)

(2) \(4 \mathrm{~cm}\)

(3) \(6 \mathrm{~cm}\)

(4) \(36 \mathrm{~cm}\)

Q.46 An object is placed at a distance of \(5 \mathrm{~cm}\) from a convex lens of focal length \(10 \mathrm{~cm}\), then the image is-

(1) Real, diminished and at a distance of \(10 \mathrm{~cm}\) from the lens.

(2) Real, enlarged and at a distance of \(10 \mathrm{~cm}\) from the lens.

(3) Virtual, enlarged and at a distance of \(10 \mathrm{~cm}\) from the lens.

(4) Virtual, diminished and at a distance of \(10 / 3 \mathrm{~cm}\) from the lens.

Q.47 Inside water, an air bubble behave-

(1) Always like a convex lens

(2) Always like a concave lens

(3) Always like a slab of equal thickness

(4) Sometimes concave and sometimes like a convex lens 

Q.48 In the figure given below, there are two convex lens \(\mathrm{L}_{1}\) and \(\mathrm{L}_{2}\) having focal length of \(\mathrm{f}_{1}\) and \(\mathrm{f}_{2}\) respectively. The distance between \(\mathrm{L}_{1}\) and \(\mathrm{L}_{2}\) will be

(1) \(f_{1}\)

\((2) f_{2}\)

(3) \(f_{1}+f_{2}\)

(4) \(f_{1}-f_{2}\)

Q.49 A virtual erect image by a diverging lens is represented by ( \(u, v, f\) are coordinates)

Q.50 What should be the value of distance \(\mathrm{d}\) so that final image is formed on the object itself. (focal lengths of the lenses are written on the lenses).

(1) \(10 \mathrm{~cm}\)

(2) \(20 \mathrm{~cm}\)

(3) \(5 \mathrm{~cm}\)

(4) none of these

Q.51 The ray diagram could be correct

(1) If \(\mathrm{n}_{1}=\mathrm{n}_{2}=\mathrm{n}_{\mathrm{g}}\)

(2) If \(\mathrm{n}_{1}=\mathrm{n}_{2}\) and \(\mathrm{n}_{1}<\mathrm{n}_{\mathrm{g}}\)

(3) If \(\mathrm{n}_{1}=\mathrm{n}_{2}\) and \(\mathrm{n}_{1}>\mathrm{n}_{\mathrm{g}}\)

(4) Under no circumstances

Q.52 A glass lens is placed in a medium in which it is found to behave like a glas plate. Refractive index of the medium will be :

(1) Greater than the refractive index of glass

(2) Smaller than the refractive index of glass

(3) Equal to refractive index of glass

(4) No case will be possible from above

Q.53 A biconvex lens forms a real image of an object placed perpendicular to its principal axis. Suppose the radii of curvature of the lens tend to infinity. Then the image would

(1) Disappear

(2) Remain as real image still

(3) Be virtual and of the same size as the object (4)

(4) Suffer from aberrations

Q.54 If the central portion of a convex lens is wrapped in black paper as shown in the figure

(1) No image will be formed by the remaining portion of the lens

(2) The full image will be formed but it will be less bright

(3) The central portion of the image will be missing

(4) There will be two images each produced by one of the exposed portions of the lens Q.55 In the figure, an air lens of radii of curvature \(10 \mathrm{~cm}\left(\mathrm{R}_{1}=\mathrm{R}_{2}=10 \mathrm{~cm}\right)\) is cut in a cylinder of glass \((\mu=1.5)\). The focal length and the nature of the lens is

(1) \(15 \mathrm{~cm}\), concave

(2) \(15 \mathrm{~cm}\), convex

(3) \(\infty\), neither concave nor convex

(4) 0 , concave

Q.56 Two thin lenses of power \(+5 \mathrm{D}\) and \(-2 \mathrm{D}\) are placed in contact with each other. Focal length of the combination will behave like a-

(1) Convex lens of focal length \(3 \mathrm{~m}\)

(2) Concave lens of focal length \(0.33 \mathrm{~m}\)

(3) Convex lens of focal length \(0.33 \mathrm{~m}\)

(4) None of the above

Q.57 A combination of two thin lenses with focal lengths \(\mathrm{f}_{1}\) and \(\mathrm{f}_{2}\) respectively forms an image of distant object at distance \(60 \mathrm{~cm}\) when lenses are in contact. The position of this image shifts by \(30 \mathrm{~cm}\) towards the combination when two lenses are separated by \(10 \mathrm{~cm}\). The corresponding values of \(f_{1}\) and \(f_{2}\) are

(1) \(30 \mathrm{~cm},-60 \mathrm{~cm}\)

(2) \(20 \mathrm{~cm},-30 \mathrm{~cm}\)

(3) \(15 \mathrm{~cm},-20 \mathrm{~cm}\)

(4) \(12 \mathrm{~cm},-15 \mathrm{~cm}\)

Q.58 A plano convex lens \((\mathrm{f}=20 \mathrm{~cm})\) is silvered at plane surface. Now f will be

(1) \(20 \mathrm{~cm}\)

(2) \(40 \mathrm{~cm}\)

(3) \(30 \mathrm{~cm}\)

(4) \(10 \mathrm{~cm}\)

Q.59 A luminous object is placed at a distance of \(30 \mathrm{~cm}\) from a convex lens of focal length \(20 \mathrm{~cm}\). On the other side of the lens, at what distance from the lens must a convex mirror of radius of curvature \(10 \mathrm{~cm}\) be placed in order to have and upright image of the object coincident with it ?

(1) \(12 \mathrm{~cm}\)

(2) \(30 \mathrm{~cm}\)

(3) \(50 \mathrm{~cm}\)

(4) \(60 \mathrm{~cm}\)

Q.60 The plane surface of a plano - convex lens of focal lenght \(f\) is silvered. It will behave as:

(1) plane mirror

(2) convex mirror of focal length \(2 \mathrm{f}\)

(3) concave mirror of focal length \(\mathrm{f} / 2\)

(4) none of the above

Q.61 When light is passed through a prism, the colour which deviates least is:

(1) Red

(2) violet

(3) Blue

(4) Green

Q.62 If refractive index of red, violet and yellow lights are \(1.42,1.62\) and 1.50 respectively for a medium, its dispersive power will be -

(1) 0.4

(2) 0.3

(3) 0.2

(4) 0.1

Q.63 A plane glass slab is placed over various coloured letters. The letter which appears to be raised the least is:

(1) violet

(2) yellow

(3) red

(4) green

Q.64 A medium has \(\mathrm{n}_{\mathrm{v}}=1.56, \mathrm{n}_{\mathrm{r}}=1.44\). Then its dispersive power is:

(1) \(3 / 50\)

(2) \(6 / 25\)

(3) 0.03

(4) none of these

Q.65 The ratio of angle of minimum deviation of a prism in air and when dipped in water will be \(\left({ }_{\mathrm{a}} \mu_{\mathrm{g}}=3 / 2\right.\) and \(\left.{ }_{\mathrm{a}} \mu_{\mathrm{w}}=4 / 3\right)\)

If prism angle is very small

(1) \(1 / 8\)

(2) \(1 / 2\)

(3) \(3 / 4\)

(4) \(1 / 4\)

Q.66 The respective angle of the flint and crown glass prisms are A' and A. They are to be used for dispersion without deviation, then the ratio of their angles A'/A will be

(1) \(-\frac{\left(\mu_{\mathrm{y}}-1\right)}{\left(\mu_{\left.y^{\prime}-1\right)}\right.}\)

(2) \(-\frac{\left(\mu_{y}{ }^{\prime}-1\right)}{\left(\mu_{y}-1\right)}\)

(3) \(\left(\mu_{y}^{\prime}-1\right)\)

(4) \(\left(\mu_{y}-1\right)\) 

\section{GEOMETRICAL OPTICS}

Q.67 A person can see clearly only upto a distance of \(25 \mathrm{~cm}\). He wants to read a book placed at a distance of \(50 \mathrm{~cm}\). What kind of lens does he required for his spectacles and what must be its power?

(1) concave, \(-1.0 \mathrm{D}\)

(2) Convex, +1.5 D

(3) Concave, \(-2.0 \mathrm{D}\)

(4) Convex, \(+2.0 \mathrm{D}\)

Q.68 Astigmatism (for a human eye) can be removed by using

(1) Concave lens

(2) Convex lens

(3) Cylindrical lens

(4) Prismatic lens

Q.69 In a compound microscope, the intermediate image is -

(1) virtual, erect and magnified

(2) real, erect and magnified

(3) real, inverted and magnified

(4) virtual, erect and reduced

Q.70 The resolving power of a telescope is more when its objective lens has

(1) greater focal length (2) smaller focal length (3) greater diameter \(\quad\) (4) smaller diameter

Q.71 A Galileo telescope has an objective of focal length \(100 \mathrm{~cm} \&\) magnifying power 50 . The distance between the two lenses in normal adjustment will be

(1) \(150 \mathrm{~cm}\)

(2) \(100 \mathrm{~cm}\)

(3) \(98 \mathrm{~cm}\)

(4) \(200 \mathrm{~cm}\)

Q.72 The convex lens is used in-

(1) Microscope

(2) Telescope

(3) Projector

(4) All of the above

Q.73 An astronomical telescope has an eyepiece of focal-length \(5 \mathrm{~cm}\). If the angular magnification in normal adjustment is 10 , when final image is at least distance of distinct vision \((25 \mathrm{~cm})\) from eye piece, then angular magnification will be :

(1) 10

(2) 12

(3) 50

(4) 60

Q.74 A person with a defective sight is using a lens having a power of \(+2 \mathrm{D}\). The lens he is using is

(1) concave lens with \(f=0.5 \mathrm{~m}\)

(3) concave lens with \(f=0.2 \mathrm{~m}\)

(2) convex lens with \(f=2.0 \mathrm{~m}\)

(4) convex lens with \(f=0.5 \mathrm{~m}\)

Q.75 The focal lengths of the objective and eye-lens of a microscope are \(1 \mathrm{~cm}\) and \(5 \mathrm{~cm}\) respectively. If the magnifying power for the relaxed eye is 45 , then the length of the tube is :

(1) \(30 \mathrm{~cm}\)

(2) \(25 \mathrm{~cm}\)

(3) \(15 \mathrm{~cm}\)

(4) \(12 \mathrm{~cm}\)

Q.76 The focal length of the objective lens of a compound microscope is :

(1) Equal to the focal length of its eye piece (2) Less than the focal length of eye piece

(3) Greater than the focal length of eye piece (4) Any of the above three

Q.77 When the object is self-luminous, the resolving power of a microscope is given by expression :

(1) \(\frac{2 \mu \sin \theta}{1.22 \lambda}\)

(2) \(\frac{\mu \sin \theta}{\lambda}\)

(3) \(\frac{2 \mu \cos \theta}{1.22 \lambda}\)

(4) \(\frac{2 \mu}{\lambda}\)

Q.78 the focal length of objective and eye lens of a stronomical telescope are respectively \(2 \mathrm{~m}\) and \(5 \mathrm{~cm}\). Final image is formed at

(i) least distance of distinct vision

(ii) infinity. The magnifying power in both cases will be:

(1) \(-48,-40\)

(2) \(-40,-48\)

(3) \(-40,48\)

(4) \(-48,40\)

Q.79 An astronomical telescope has an angular magnification of magnitude 5 for distant objects. The seperation between the objective and the eye piece is \(36 \mathrm{~cm}\) and the final image is formed at infinity. The focal length \(f_{0}\) of the objective and the focal length \(f_{e}\) of the eye piece are :

(1) \(f_{0}=45 \mathrm{~cm}\) and \(f_{\mathrm{e}}=-9 \mathrm{~cm}\)

(3) \(f_{0}=50 \mathrm{~cm}\) and \(f_{e}=10 \mathrm{~cm}\)

(2) \(\mathrm{f}_{0}=7.2 \mathrm{~cm}\) and \(\mathrm{f}_{\mathrm{e}}=5 \mathrm{~cm}\)

(4) \(f_{0}=30 \mathrm{~cm}\) and \(\mathrm{f}_{\mathrm{e}}^{\mathrm{e}}=6 \mathrm{~cm}\)