A radioactive nucleus emits a beta particle. Its mass number MCQ with Answer and Explanation

A radioactive nucleus emits a beta particle. Its mass number
A. Decreases by 2
B. Increases by 1
C. Decreases by 1
D. Remains unchanged
Answer: Option D
Solution (By JKSSB Mock Tests)
β⁻ decay: n → p + e⁻, so A unchanged, Z increases by 1.

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Practice More Physics Questions

Question #1
The slope of a velocity-time graph gives
A. Distance
B. Speed
C. Acceleration
D. Displacement

Correct Answer: Option C


Explanation:
Slope = dv/dt = acceleration. Area under v-t gives displacement. Often confused.

This question belongs to: Science Physics
Question #2
The phenomenon of dispersion of light occurs because:
A. Different colors have different frequencies
B. Total internal reflection occurs
C. Different colors travel at different speeds in medium
D. Prism absorbs some colors

Correct Answer: Option C


Explanation:
Dispersion (splitting of white light into colors) occurs because refractive index n varies with wavelength (Cauchy's relation: n ∝ 1/λ² approximately). Since v = c/n, different colors travel at different speeds in the medium, causing different refraction angles (Snell's law). Frequency remains constant across media. Memory tip: 'Dispersion: n(λ) ⇒ v(λ) ⇒ different bending; violet bends most (highest n)'. This optics concept is frequently tested in competitive exams. Always distinguish cause (speed variation) from property (frequency/wavelength); competitive exams often test this nuanced understanding.

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Question #3
A 50 kg man climbs 30 steps each 20 cm high in 10 s. His power (g=10 m/s²) is
A. 30 W
B. 150 W
C. 300 W
D. 600 W

Correct Answer: Option C


Explanation:
Total height = 30 × 0.2 m = 6 m. Work done = mgh = 50 × 10 × 6 = 3000 J. Power = Work/time = 3000/10 = 300 W. If steps height and number given, calculate total vertical displacement. Time taken for climbing is important. Power is rate of doing work.

This question belongs to: Science Physics