Resolving power = 1/(1.22λ/2NA). It depends on wavelength and numerical aperture (NA = n×sin(θ))
Q.10Medium
When white light passes through a prism, violet light deviates more than red light. This is because:
Answer: D
Higher frequency → higher refractive index → slower speed in medium → greater deviation. All statements are correct.
Q.11Medium
An object is placed 10 cm from a concave lens of focal length 20 cm. Find the magnification.
Answer: C
Using lens formula: 1/(-20) = 101 + 1/v. v = -6.67 cm. Magnification m = -v/u = 6.1067 = 0.67
Q.12Medium
Polarization of light proves that light is:
Answer: B
Only transverse waves can be polarized. Polarization demonstrates the transverse nature of electromagnetic waves.
Q.13Easy
A thin lens has power +5 diopters. Find its focal length.
Answer: A
Power P = 1/f. f = 51 = 0.2 m = 20 cm. Positive power indicates convex lens.
Q.14Hard
In Young's double slit experiment, if one slit is covered with a transparent film of thickness t and refractive index μ, the path difference changes by:
Answer: A
Optical path = μt, geometrical path = t. Additional path difference = μt - t = (μ-1)t
Q.15Medium
The intensity at a point in the interference pattern of two coherent sources is I₁ and I₂. The resultant intensity is maximum when the phase difference is:
Answer: B
Maximum intensity occurs for constructive interference when phase difference = 0 or 2π. I_max = (√I₁ + √I₂)²
Q.16Hard
When a convex lens is immersed in water (n=34), its focal length compared to air is:
Answer: A
Lens maker's formula: 1/f = (n_lens/n_medium - 1)(1/R₁ - 1/R₂). When medium changes from air to water, (n_lens/n_medium) decreases, so f increases.
Q.17Hard
The minimum deviation through a prism occurs when:
Answer: D
All three conditions are equivalent and occur at minimum deviation: symmetric path, equal angles, and ray parallel to base.
Q.18Hard
The Brewster angle for glass-air interface (n_glass = 1.5) is approximately:
Answer: C
tan(θ_B) = n = 1.5. θ_B = arctan(1.5) = 56.31°. At this angle, reflected light is completely polarized.
Q.19Easy
A ray of light travels from medium 1 (refractive index n₁ = 1.5) to medium 2 (refractive index n₂ = 1.0). If the angle of incidence is 30°, what is the angle of refraction?
Answer: A
Using Snell's law: n₁sin(θ₁) = n₂sin(θ₂). So 1.5 × sin(30°) = 1.0 × sin(θ₂). This gives sin(θ₂) = 0.75, therefore θ₂ = 48.6°
Q.20Easy
A concave mirror produces a real, inverted, and magnified image. Where is the object located?
Answer: A
For a concave mirror, when object is between F and C, the image is real, inverted, and magnified. This is the magnification region used in shaving mirrors.