Ray Optics and Optical Instruments · Question 21

Distance between an object and three times magnified real image is 40 cm. The focal length of the mirror used is cm.

1. -20
2. -15/2
3. -10
4. -15

Five persons P1, P2, P3, P4 and P5 recorded object distance (u) and image distance (v) using same convex lens having power +5 D as (25, 96), (30, 62), (35, 37), (45, 35) and (50, 32) respectively. Identify correct statement

1. Readings recorded by P3 and P2 persons are incorrect
2. Readings recorded by all persons are correct
3. Readings recorded by P3 person are incorrect
4. Readings recorded by P4 and P5 persons are incorrect

A thin prism with angle 5 of refractive index 1.72 is combined with another prism of refractive index 1.9 to produce dispersion without deviation. The angle of second prism is .

1. 5
2. 4
3. 4.5
4. 6

Consider light travelling from a medium A to medium B separated by a plane interface. If the light undergoes total internal reflection during its travel from medium A to B and the speed of light in media A and B are 2.4 108 m/s and 2.7 108 m/s, respectively, then the value of critical angle is :

1. -1 ( 89 )
2. -1 ( 98 )
3. -1 ( 3 13 )
4. -1 ( 8 17 )

A prism of angle 75 and refractive index 3 is coated with thin film of refractive index 1.5 only at the back exit surface. To have total internal reflection at the back exit surface the incident angle must be ( 15 = 0.25 and 25 = 0.43)

1. between 15 and 20
2. 15
3. < 15
4. > 25

The size of the images of an object, formed by a thin lens are equal when the object is placed at two different positions 8 cm and 24 cm from the lens. The focal length of the lens is cm.

A thin convex lens of focal length 5 cm and a thin concave lens of focal length 4 cm are combined together (without any gap) and this combination has magnification m1 when an object is placed 10 cm before the convex lens. Keeping the positions of convex lens and object undisturbed a gap of 1 cm is introduced between the lenses by moving the concave lens away, which leads to a change in magnification of total lens system to m2. The value of | m1m2 | is .

1. 2527
2. 56
3. 527
4. 32

Consider an equilateral prism (refractive index 2). A ray of light is incident on its one surface at a certain angle i. If the emergent ray is found to graze along the other surface then the angle of refraction at the incident surface is close to

1. 30
2. 20
3. 40
4. 15

A parallel beam of light travelling in air (refractive index 1.0) is incident on a convex spherical glass surface of radius of curvature 50 cm. Refractive index of glass is 1.5. The rays converge to a point at a distance x cm from the centre of curvature of the spherical surface. The value of x is cm.

The wavelength of light, while it is passing through water is 540 nm. The refractive index of water is 4/3. The wavelength of the same light when it is passing through a transparent medium having refractive index of 3/2 is nm.

1. 540
2. 840
3. 480
4. 380