The Cauchy's dispersion formula is

• n = A + Bλ^-2 + Cλ^-4

• n = A + Bλ^-2 + Cλ⁴

• n = A + Bλ² + Cλ^-4

• n = A + Bλ² + Cλ⁴

Golden view of sea shell is due to

• diffraction

• polarisation

• dispersion

• reflection

The working of which of the following is similar to that of a slide projector?

• Electron microscope

• Scanning electron microscope

• Transmission electron microscope

• Atomic force microscope

A ray of light is traveling from glass to air, (refractive index of glass= 1.5). The angle of incidence is 50°. The deviation of the ray is

• 0°

• 80°

• $50° - {\sin }^{-1}\left[\frac{\sin 50°}{1.5}\right]$

• ${\sin }^{-1}\left[\frac{\sin 50°}{1.5}\right] - 50°$

Magnification of a compound microscope is 30. The focal length of eye-piece is 5 cm and the image is formed at a distance of distinct vision of 25 cm. The magnification of the objective lens is:

• 6

• 5

• 7.5

• 10

A ray falls on a prism ABC (AB = BC) and travels as shown in the figure. The least value of the refractive index of the material of the prism should be;

• 1.5

• $\sqrt{2}$

• 1.33

• $\sqrt{3}$

137.

A flat mirror revolves at a constant angular velocity making 2 revolutions/s. With what velocity will a light spot move along a spherical screen with a radius of 10 m if the mirror is at a centre of curvature of the screen?

• 251.2 m/s

• 261.2 m/s

• 271.2 m/s

• 241.2 m/s

A vessel consists of two plane mirrors at right angles (as shown in the figure). The vessel is filled with water. The total deviation in incident ray is

• 0°

• 90°

• 180°

• none of these

An object is placed at a distance equal to the focal length of a convex mirror. If the focal length of the mirror is f, then the distance of the image from the pole of the mirror is :

• less than f

• equal to f

• more than f

• infinity

A person standing in front of a mirror finds his image larger than himself. This implies that the mirror is :

• convex

• parabolic

• plane

• concave