Ray Optics and Optical Instruments

Identify the mismatch in the following

• Myopia  —  Concave lens

• For rear view  —  Concave mirror

• Hypermetropia  —  Convex lens

• Astigmatism  —  Cylindrical lens

The focal lengths of the objective and the eyepiece of the telescope are 225 cm and 5 cm respectively. The magnifying power of the telescope will be

• 49

• 45

• 35

• 60

The angle of incidence for an equilateral prism of refractive index $\sqrt{3}$ so that the ray is parallel to the base inside the prism is

• 30°

• 20°

• 60°

• 45°

According to Rayleigh scattering law, the amount of scattering is

• directly proportional to wavelength of light

• directly proportional to square of wavelength of light

• inversely proportional to fourth power of wavelength of light

• inversely proportional to wavelength of light

An object is kept at a distance of 60 cm from a concave mirror. For getting a magnification of $\frac{1}{2}$, focal length of the concave mirror required is

• 20 cm

• 40 cm

• − 20 cm

• 30 cm

If the speed of light in material A is 1.25 times its speed in material B, then the ratio of the refractive indices of these materials is

• 1.50

• 1.00

• 0.800

• 1.25

The resolving power of a microscope is

• inversely proportional to numerical aperture

• directly proportional to wavelength

• directly proportional to square of the wavelength

• directly proportional to numerical aperture.

The focal length of the lens of refractive index (µ = 1.5) in air is 10 cm. If air is replaced by water of $\mathrm{\mu } = \frac{4}{3}$, its focal length is

• 20 cm

• 30 cm

• 40 cm

• 25 cm

A beam of natural light falls on a system of 5 polaroids, which are arranged in succession such that the pass axis of each polaroid is turned through 60° with respect to the preceding one. The fraction of the incident light intensity that passes through the system is 

• $\frac{1}{64}$

• $\frac{1}{32}$

• $\frac{1}{512}$

• $\frac{1}{128}$

A glass prism of refractive index 1.5 is immersed in water $\left(\mathrm{\mu } = \frac{4}{3}\right)$. Refer figure.

A light beam incident normally on the face AB is totally reflected to reach the face BC, if

• 2/3 < sin θ < 8/9

• sin θ ≤ 2/3

• cos θ ≥ 8/9

• sin θ > 8/9