Assertion (A): A convex mirror is used as a rear-view mirror. Reason (R): It gives a wider field of view. MCQ with Answer and Explanation

Assertion (A): A convex mirror is used as a rear-view mirror. Reason (R): It gives a wider field of view.
A. Both A and R true, R not correct explanation
B. Both A and R true, R correct explanation
C. A true, R false
D. A false, R true
Answer: Option B
Solution (By JKSSB Mock Tests)
Convex mirror provides wider field and erect image, so R explains A correctly.

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Practice More Physics Questions

Question #1
The work function of a metal is 2.3 eV. The threshold frequency for photoelectric emission is approximately: (h = 4.14×10⁻¹⁵ eV·s)
A. 1.2×10¹⁵ Hz
B. 5.6×10¹⁴ Hz
C. 8.0×10¹⁴ Hz
D. 3.5×10¹⁴ Hz

Correct Answer: Option B


Explanation:
Photoelectric equation: work function φ = hν₀, where ν₀ is threshold frequency. Thus ν₀ = φ/h = 2.3 eV / (4.14×10⁻¹⁵ eV·s) ≈ 5.555×10¹⁴ Hz ≈ 5.6×10¹⁴ Hz. This direct application tests photoelectric effect fundamentals. Memory aid: 'ν₀ = φ/h; higher work function ⇒ higher threshold frequency'. Competitive exams frequently provide h in eV·s for such calculations. Always ensure units match: eV for φ and h to avoid conversion errors. This problem assesses numerical proficiency in modern physics applications.

This question belongs to: Science Physics
Question #2
The direction of magnetic field around a straight current-carrying wire is given by
A. Fleming's right hand rule
B. Fleming's left hand rule
C. Ohm's law
D. Right hand thumb rule

Correct Answer: Option D


Explanation:
Right hand thumb rule: thumb current, fingers curl gives field direction.

This question belongs to: Science Physics
Question #3
The loudness of sound depends on
A. Wavelength
B. Speed
C. Frequency
D. Amplitude

Correct Answer: Option D


Explanation:
Loudness correlates with intensity, which is proportional to square of amplitude. Frequency determines pitch. Larger amplitude → louder sound. Measured in decibels.

This question belongs to: Science Physics