151.

A microscope is having objective of focal length 1 cm and eyepiece of focal length 6 cm. If tube length is 30 cm and image is formed at the least distance of distinct vision, what is the magnification produced by the microscope. Take D = 25cm.

• 6

• 150

• 25

• 125

Diameter of the objective of a telescope is 200 cm. What is the resolving power of a telescope ? Take wavelength of light = $5000 \stackrel{\circ }{\mathrm{A}}$.

• 6.56 × 10⁶

• 3.28 × 10⁵

• 1 × 10⁶

• 3.28 × 10⁶

Calculate the focal length of a reading glass of a person if the distance of distinct vision is 75 cm.

• 75.2 cm

• 25.6 cm

• 100.4 cm

• 37.5 cm

A person wants a real image of his own, 3 times enlarged. Where should he stand infront of a concave mirror of radius of curvature of 30 cm ?

• − 90 cm

• − 10 cm

• − 20 cm

• − 30 cm

If ε₀ and µ₀ are the permittivity and permeability of free space and ε and μ are the corresponding quantities for a medium. Then, refractive index of the medium is

• 1

• $\sqrt{\frac{{\mathrm{\mu }}_0{\mathrm{\epsilon }}_0}{\mathrm{\mu \epsilon }}}$

• insufficient information

• $\sqrt{\frac{\mathrm{\mu \epsilon }}{{\mathrm{\mu }}_0{\mathrm{\epsilon }}_0}}$

A plane glass plate is placed over a various coloured letters (violet, green, yellow, red). The letter which appears to raised more is

• red

• yellow

• green

• violet

A ray of light passes through four transparent media with refractive index n₁, n₂, n₃ and n₄ as shown in the figure. The surfaces of all media are parallel.

If the emergent ray DE is parallel to incident ray AB, then

• n₁ = n₄ 

• n₂ = n₄

• n₃ = n₄

• ${\mathrm{n}}_1 = \frac{{\mathrm{n}}_2 + {\mathrm{n}}_3 + {\mathrm{n}}_4}{3}$

Focal length of a convex lens is 20 cm and its refractive index is 1.5. It produces an erect, enlarged image if the distance of the object from the lens is

• 40 cm

• 30 cm

• 15 cm

• 20 cm

A ray of light suffers a minimum deviation when incident on an equilateral prism of refractive index $\sqrt{2}$. The angle of deviation is

• 30°

• 45°

• 60°

• 50°

For what distance ray optics is good approximation when the aperture is 4 mm and the wavelength of light is 400 nm ?

• 24 m

• 40 m

• 18 m

• 30 m