Focal lengths of objective and eyepiece of a compound microscope are 2 cm and 6.25 cm respectively. An object AB is placed at a distance of 2.5 cm from the objective which forms the image B'A' as shown in the figure. Maximum magnifying power in this case is :
1. 10
2. 20
3. 5
4. 25
Two identical equiconvex thin lenses each of focal lengths 20 cm, made of material of refractive index 1.5 are placed coaxially in contact as shown. Now, the space between them is filled with a liquid with a refractive index of 1.5. The equivalent power of this arrangement will be:
1. | +5 D | 2. | zero |
3. | +2.5 D | 4. | +0.5 D |
The focal length of the plano-convex lens is 20 cm. If its plane surface is silvered, then
1. it behaves as a concave mirror of focal length 10 cm
2. it behaves as a convex mirror of focal length of 10 cm
3. it behaves as a concave mirror of focal length 20 cm
4. none of these
A concave mirror of focal length \(100\) cm is used to obtain the image of the sun which subtends an angle of \(30'.\) The diameter of the image of the sun will be:
1. \(1.74\) cm
2. \(0.87\) cm
3. \(0.435\) cm
4. \(100\) cm
A square of side 3 cm is placed at a distance of 25 cm from a concave mirror of focal length 10 cm. The centre of the square is at the axis of the mirror and the plane is normal to the axis. The area enclosed by the image of the square is:
1. | \(4 \mathrm{~cm}^2 \) | 2. | \(6 \mathrm{~cm}^2 \) |
3. | \(16 \mathrm{~cm}^2 \) | 4. | \(36 \mathrm{~cm}^2 \) |
Two transparent slabs have the same thickness as shown. One is made of material A of refractive index 1.5. The other is made of two materials B and C with thickness in the ratio 1:2. The refractive index of C is 1.6. If a monochromatic parallel beam passing through the slabs has the same number of waves inside both, the refractive index of B is
1. 1.1
2. 1.2
3. 1.3
4. 1.4
A rectangular glass slab ABCD, of refractive index , is immersed in water of the refractive index . A ray of light is incident at the surface AB of the slab as shown. The maximum value of the angle of incidence , such that the ray comes out only from the other surface CD is given by
1.
2.
3.
4.
A rod of glass ( = 1.5) and of the square cross-section is bent into the shape as shown. A parallel beam of light falls on the plane flat surface A as shown in the figure. If d is the width of a side and R is the radius of a circular arc then for what maximum value of , light entering the glass slab through surface A will emerge from the glass through B?
1. | 1.5 | 2. | 0.5 |
3. | 1.3 | 4. | None of these |
A concave mirror is placed at the bottom of an empty tank with face upwards and axis vertical. When sunlight falls normally on the mirror, it is focused at distance of 32 cm from the mirror. If the tank is filled with water upto a height of 20 cm, then the sunlight will now get focussed at
(1) 16 cm above water level
(2) 9 cm above water level
(3) 24 cm below water level
(4) 9 cm below water level
The distance between a convex lens and a plane mirror is 10 cm. The parallel rays incident on the convex lens, after reflection from the mirror form image at the optical centre of the lens. Focal length of the lens will be:
1. | 10 cm | 2. | 20 cm |
3. | 30 cm | 4. | Cannot be determined |
The focal length of the objective lens and the eye lens is 4 mm and 25 mm respectively in a compound microscope. The distance between objective and eyepiece lens is 16 cm. Find its magnifying power for relaxed eye position-
1. 32.75
2. 327.5
3. 0.3275
4. None of the above
An observer can see through a pinhole the top end of a thin rod of height h, placed as shown in the figure. The beaker height is 3h and its radius h. When the beaker is filled with a liquid up to a height 2h, he can see the lower end of the rod. Then the refractive index of the liquid is
(1)
(2)
(3)
(4) 3/2
The graph between u and v for a convex mirror is:
1. | 2. | ||
3. | 4. |
A medium shows relation between i and r as shown. If speed of light in the medium is nc then value of n is
(1) 1.5
(2) 2
(3) 2–1
(4) 3–1/2
For a concave mirror, if the virtual image is formed, the graph between m and u is of the form :
A luminous object is placed at a distance of 30 cm from the convex lens with a focal length of 20 cm. On the other side of the lens, at what distance from the lens, a convex mirror with a radius of curvature of 10 cm be placed in order to have an upright image of the object coincident with it?
1. | 12 cm | 2. | 30 cm |
3. | 50 cm | 4. | 60 cm |
The size of the image of an object, which is at infinity, as formed by a convex lens of
focal length 30 cm is 2 cm. If a concave lens of focal length 20 cm is placed between the
convex lens and the image is at a distance of 26 cm from the convex lens, calculate the
new size of the image.
1. 1.25 cm
2. 2.5 cm
3. 1.05 cm
4. 2 cm
An achromatic prism is made by crown glass prism and flint glass prism
. If and , then resultant deviation for red coloured ray will
be
1. 1.04°
2. 5°
3. 0.96°
4. 13.5°
An isosceles prism of angle 120° has a refractive index of 1.44. Two parallel
monochromatic rays enter the prism parallel to each other in air as shown. The rays
emerging from the opposite faces :
1. Are parallel to each other
2. Are diverging
3. Make an angle with each other
4. Make an angle with each other
A ray of light is incident on the hypotenuse of a right-angled prism after travelling parallel
to the base inside the prism. If is the refractive index of the material of the prism, the
maximum value of the base angle for which light is totally reflected from the hypotenuse
is
1.
2.
3.
4.
A plano-convex lens when silvered in the plane side behaves like a concave mirror of
focal length 30 cm. However, when silvered on the convex side it behaves like a concave
mirror of focal length 10 cm. Then the refractive index of its material will be
1. 3.0
2. 2.0
3. 2.5
4. 1.5
A ray of light travels from an optically denser to rarer medium. The critical angle for the
two media is C. The maximum possible deviation of the ray will be
1.
2. 2C
3.
4.
A point object is moving on the principal axis of a concave mirror of focal length 24 cm towards the mirror. When it is at a distance of 60 cm from the mirror, its velocity is 9 cm/sec. What is the velocity of the image at that instant?
1. | 5 cm/sec towards the mirror |
2. | 4 cm/sec towards the mirror |
3. | 4 cm/sec away from the mirror |
4. | 9 cm/sec away from the mirror |
A thin prism having refracting angle is made of glass of refractive index 1.42. This prism is combined with another thin prism of glass of refractive index 1.7. This combination produces dispersion without deviation. The refracting angle of second prism should be
(1)
(2)
(3)
(4)
Two identical glass equi-convex lenses of focal length each are kept in contact. The space between the two lenses is filled with water . The focal length of the combination is
(a) (b)
(c) (d)
A person can see clearly objects only when they lie between 50 cm and 400 cm from his eyes. In order to increase the maximum distance of distinct vision to infinity, the type and power of the correcting lens, the person has to use will be-
1. convex, +2.25 diopter
2. concave, - 0.25 diopter
3. concave, - 0.2 diopter
4. convex, + 0.15 diopter
An astronomical telescope has an objective and eyepiece of focal lengths 40 cm and 4 cm respectively. To view an object 200 cm away from the objective, the lenses must be separated by a distance of :
(1) 46.0 cm
(2) 50.0 cm
(3) 54.0 cm
(4) 37.3 cm
Match the corresponding entries of Column 1 with Column 2. [Where m is the magnification produced by the mirror]
Column 1 Column 2
A. m=-2 a. Convex mirror
B. m=-1/2 b. Concave mirror
C. m=+2 c. Real image
D. m=+1/2 d. Virtual Image
(1)A->a and c;B->a and d; C->a and b; D->c and d
(2)A->a and d; B->b and c; C->b and d; D-> b and c
(3)A->c and d; B->b and d;C->b and c;D->a and d
(4)A->b and c; B->b and c; C->b and d; D->a and d
The refracting angle of a prism is \(\text{A}\), and refractive index of the material of the prism is cot(A/2). The angle of minimum deviation is:
1. \(180^{\circ}-3\text{A}\)
2. \(180^{\circ}-2\text{A}\)
3. \(90^{\circ}-\text{A}\)
4. \(180^{\circ}+2\text{A}\)
In an astronomical telescope in normal adjustment a straight black line of length L is drawn on inside part of the objective lens. The eye-piece forms a real image of this line. The length of this image is l. The magnification of the telescope is:
(1)L/l+1
(2)L/l-1
(3)L+1/L-1
(4)L/l
A beam of light consisting of red, green and blue colours is incident on a right angled prism. The refractive index of the material of the prism for the above red, green and blue wavelengths are 1.39, 1.44 and 1.47, respectively.
The prism will
(a) separate the blue colour part from the red and green colours
(b) separate all the three colours from one another
(c) not separate the three colours at all
(d) separate the red colour part from the green and blue colours
A plane-convex lens fits exactly into a plano-concave lens. Their plane surfaces are parallel to each other. If lenses are made of different materials of refractive indices μ1 and μ2 and R is the radius of curvature of the curved surface of the lenses, then the focal length of the combination is:
1. R/2(μ1 + μ2)
2. R/2(μ1 - μ2)
3. R/(μ1 - μ2)
4. 2R/(μ2 - μ1)
For a normal eye, the cornea of eye provides a converging power of 40 D and the least converging power of the eye lens behind the cornea is 20 D. Using this information, the distance between the retina and the cornea-eye lens can be estimated to be
(1) 5 cm
(2) 25 cm
(3) 1.67 cm
(4) 1.5 cm
A ray of light is incident at an angle of incidence, i, on one face of a prism of angle A (assumed to be small) and emerges normally from the opposite face.If the refractive index of the prism is the angle of incidence i, is nearly equal to
(1)
(2)
(3)
(4)
A concave mirror of focal length is placed at a distance of d from a convex lens of focal length A beam of light coming from infinity and falling on this convex lens concave mirror combination returns to infinity. The distance d must be equal to-
(1)
(2)
(3)
(4)
The magnifying power of a telescope is 9. When it is adjusted for parallel rays the distance between the objective and eyepiece is 20cm. The focal length of lenses are
(1) 10cm,10cm
(2) 15cm,5cm
(3) 18cm,2cm
(4) 11cm,9cm
For the angle of minimum deviation of a prism to be equal to its refracting angle, the prism must be made of a material whose refractive index
(1) lies between and 1
(2) lies between 2 and
(3) is less than 1
(4) is greater than 2
A rod of length 10 cm lies along the principal axis of a concave mirror of focal length 10 cm in such a way that its end closer to the pole is 20 cm away from the mirror. The length of the image is:
1. | 10 cm | 2. | 15 cm |
3. | 2.5 cm | 4. | 5 cm |
A biconvex lens of refractive index 1.5, has a radius of curvature of magnitude 20 cm. Which one of the following options describes best the image formed of an object of height 2 cm placed 30 cm from the lens?
(1) Virtual, upright, height=0.5 cm
(2) Real, inverted, height=4 cm
(3) Real, inverted, height=1 cm
(4) Virtual, upright, height=1 cm
A thin prism of angle made of glass of refractive index is combined with another prism of glass of refractive index The combination of the prism produces dispersion without deviation. The angle of the second prism should be
(1)
(2)
(3)
(4)
A converging beam of rays is incident on a diverging lens. Having passed though the lens the rays intersect at a point 15cm from the lens on the opposite side. If the lens is removed the point where the rays meet will move 5cm closer to the lens. The focal length of the lens is:
(1) -10cm
(2) 20cm
(3) -30cm
(4) 5cm
The speed of light in media and is and respectively. A ray of light enters from medium to at an incidence angle i. If the ray suffers total internal reflection, the value of i is
(1) equal to
(2) equal to or less than
(3) equal to or greater than
(4) less than
A ray of light is incident on a \(60^\circ\)
1. zero
2. \(30^\circ\)
3. \(45^\circ\)
4. \(60^\circ\)
Two thin lenses of focal length are in contact and coaxial. The power of the combination is
(1)
(2)
(3)
(4)
A boy is trying to start a fire by focusing sunlight on a piece of paper using an equiconvex lens of focal length 10 cm. The diameter of the sun is 1.39 and its mean distance from the earth is . What is the diameter of the sun's image on the paper?
1.
2.
3.
4.