air at an angle a on the side PQ of a right angled

5 Prism angle of glass prism is 10 It s refractive index of red and violet colour is 1 51 and 1 52 respectively Then its dispersive power will be 1 0 015 2 0 020 3 0 011 4 0 019

Question 14 A simple screw jack used in actual practice is A non reversible machine A reversible machine An ideal machine not a lifting machine

A converging lens of focal length 15 cm and a converging mirror of focal length 20 cm are placed with their principal axes coinciding A point source S is placed on the principal axis at a distance of 12 cm from the lens as shown in figure It is found that the final beam comes out parallel to the principal axis Let the separation between the mirror and the lens be 10 x k Find k AA S 1 M S P 5

A divergent lens has a focal length of 20 cm At what distance should an object of height 4 cm from the optical centre of the lens be placed so that its image is formed 10 cm away from the lens Find the size of the image also

Q 2 A short straight object of length lies along the central axis of a spherical concave mirror at a distance X from the mirror The focal length of the mirror is F If the length of the image in the mirror is then ratio 9 is Assume X and F D w Soup ba straight X rod doja alusy v F gewann allusz t s cov on 7 1 X Boat FJS

Example 9 12 a The near point of a hypermetropic person is 75 cm from the eye What is the power of the lens required to enable the person to read clearly a book held at 25 cm from the eye b In what way does the corrective lens help the above person Does the lens magnify objects held near the eye c The above person prefers to remove the spectacles while looking at the sky Explain why Solution a u 25 cm v 75 cm 1 f 1 25 1 75 i e f 37 5 cm The corrective lens needs to have a converging power of 2 67 dioptres b The corrective lens produces a virtual image at 75 cm of an object at 25 cm The angular size of this image is the same as that of the object In this sense the lens does not magnify the object but merely brings the object to the near point of the hypermetric eye which then gets focussed on the retina However the angular size is greater than that of the same object at the near point 75 cm viewed without the spectacles c A hypermetropic eye may have normal far point i e it may have

An object is placed at a distance of 20 cm from a co axial combination of two lenses A and B The combination of the lenses forms a real image which is four times the size of the object If lens B is concave with a focal length of 48 cm then what is the nature and focal length of lens A convex 12 cm convex 6 cm O O concave 12 cm convex 18 cm

03 In a vernier callipers ten smallest divisions of the vernier scale are equal to nine smallest 10 division on the main scale If the smallest division on the main scale is half millimeter then the vernier constant is A 0 5 mm C 0 05 mm B 0 1 mm D 0 005 mm

1 A parallel beam of monochromatic light of wavelength 5000A is incident normally on a single narrow slit of width 0 001 mm The light is focussed by a convex lens on a screen placed in focal plane The first minimum will be formed for the angle of diffraction equal to a 0 b 15 1993 c 30 d 50

2 Assertion A Focal length of a spherical mirror does not dpend on the material from which mirror is made but same for the lens depends on the material of lens Reason R law of reflection does not dpend on material and surrounding but law of refraction depends on refractive index of th materials Section R