NEET Ray Optics — Set 10

Question 1

A prism of angle $ 40^\circ $ and refractive index $ 1.5 $ produces what minimum deviation?

Accepted Answer

For a thin prism: $ D_m = (n - 1) A $. $ n = 1.5 $, $ A = 40^\circ $. $ D_m = (1.5 - 1) \times 40 = 0.5 \times 40 = 20^\circ $.

Question 2

Why does a concave mirror used in a reflecting telescope require precise curvature?

Accepted Answer

The precise curvature of a concave mirror ensures that all parallel rays from a distant object converge accurately to a single focal point. Any deviation in curvature causes spherical aberration, blurring the image and reducing the telescope’s resolving power.

Question 3

Why does a convex lens produce chromatic aberration when used with white light?

Accepted Answer

Chromatic aberration occurs in a convex lens because different wavelengths of white light refract by different amounts due to the lens material’s varying refractive index for each wavelength. Shorter wavelengths (e.g., blue) focus closer than longer ones (e.g., red), causing color fringing.

NEET Physics: Ray Optics — Practice Set 10

Q1. A prism of angle \( 40^\circ \) and refractive index \( 1.5 \) produces what minimum deviation?

Q2. Why does a concave mirror used in a reflecting telescope require precise curvature?

Q3. Why does a convex lens produce chromatic aberration when used with white light?

Q4. An object is at a depth of \( 13.3 \, \text{cm} \) in a medium with refractive index \( 1.33 \). What is the apparent depth?

Q5. A convex lens (\( f = 30 \, \text{cm} \)) and a concave lens (\( f = 15 \, \text{cm} \)) are in contact. What is the effective focal length?

Q6. A ray of light passes from glass (\( n = 1.52 \)) to air at an angle of incidence of \( 45^\circ \). What happens?

Q7. A simple microscope with a focal length of \( 10 \, \text{cm} \) forms an image at \( 25 \, \text{cm} \). What is the magnification?

Q8. A prism of angle \( 60^\circ \) has a refractive index of \( 1.4 \). What is the angle of minimum deviation?

Q9. In a concave mirror, under what condition is the image formed virtual and magnified?

Q10. What is the primary advantage of using a combination of lenses in optical instruments like microscopes?

Q11. In a plane mirror, why does the image distance equal the object distance?

Q12. In a plane mirror, what property ensures that the image is not distorted?

Q13. An object at a depth of \( 19.95 \, \text{cm} \) in water (\( n = 1.33 \)) is viewed normally. What is the apparent depth?

Q14. In a refracting telescope, why does the objective lens have a larger aperture than the eyepiece?

Q15. A lens has a power of \( +2.5 \, \text{D} \). What is its focal length in centimeters?