Govt. Exams
Entrance Exams
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Topics in JEE Physics
Polarization of light proves that light is:
Correct Answer:
B. A transverse wave
EXPLANATION
Only transverse waves can be polarized. Polarization demonstrates the transverse nature of electromagnetic waves.
An object is placed 10 cm from a concave lens of focal length 20 cm. Find the magnification.
Correct Answer:
C. +0.67
EXPLANATION
Using lens formula: 1/(-20) = 1/10 + 1/v. v = -6.67 cm. Magnification m = -v/u = 6.67/10 = 0.67
When white light passes through a prism, violet light deviates more than red light. This is because:
Correct Answer:
D. All of the above
EXPLANATION
Higher frequency → higher refractive index → slower speed in medium → greater deviation. All statements are correct.
The resolving power of a microscope depends on:
Correct Answer:
B. Wavelength of light and numerical aperture
EXPLANATION
Resolving power = 1/(1.22λ/2NA). It depends on wavelength and numerical aperture (NA = n×sin(θ))
A ray of light is incident on a glass slab of thickness 5 cm and refractive index 1.6. If the incident angle is 45°, find the lateral displacement.
Correct Answer:
B. 2.16 cm
EXPLANATION
sin(θ₂) = sin(45°)/1.6 = 0.441. θ₂ = 26.19°. Lateral displacement = t×sin(θ₁-θ₂)/cos(θ₂) = 5×sin(18.81°)/cos(26.19°) ≈ 2.16 cm
A concave mirror has a focal length of 20 cm. An object is placed at the center of curvature. Where will the image form?
Correct Answer:
A. At the center of curvature
EXPLANATION
When object is at center of curvature (u = R = 2f), image forms at the same position (v = R). Magnification = -1
Two slits separated by 0.5 mm are illuminated by light of wavelength 500 nm. The distance to the screen is 1 m. Find the fringe width.
Correct Answer:
B. 1 mm
EXPLANATION
Fringe width β = λD/d = (500×10⁻⁹ × 1)/(0.5×10⁻³) = 1×10⁻³ m = 1 mm
