Radioactivity was first discovered by MCQ with Answer and Explanation

Radioactivity was first discovered by
A. Becquerel
B. Curie
C. Rutherford
D. Roentgen
Answer: Option A
Solution (By JKExamLibrary)
Henri Becquerel discovered natural radioactivity in 1896 from uranium salts. Marie and Pierre Curie later discovered radium and polonium. Rutherford classified alpha, beta rays. Roentgen discovered X-rays.

This question belongs to: Science Physics

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Practice More Physics Questions

Question #1 Report Error
A force of 10 N acts on a body of mass 2 kg initially at rest. The momentum acquired by the body after 5 seconds is:
A. 100 kg·m/s
B. 10 kg·m/s
C. 50 kg·m/s
D. 25 kg·m/s

Correct Answer: Option C


Explanation:
Force = rate of change of momentum: F = Δp/Δt. Thus Δp = F × Δt = 10 N × 5 s = 50 kg·m/s. Since initial momentum was zero (body at rest), final momentum = 50 kg·m/s. Alternatively, acceleration a = F/m = 10/2 = 5 m/s², velocity after 5s: v = u + at = 0 + 5×5 = 25 m/s, momentum p = mv = 2×25 = 50 kg·m/s. Both methods confirm. Memory tip: Impulse (FΔt) equals change in momentum. This direct application of Newton's second law is essential for dynamics problems in competitive exams.

This question belongs to: Science Physics
Question #2 Report Error
Ultrasound frequencies are typically above
A. 20 Hz
B. 2000 Hz
C. 20000 Hz
D. 200 Hz

Correct Answer: Option C


Explanation:
Human hearing range is about 20 Hz to 20 kHz. Sound above 20 kHz is ultrasound. Infrasound is below 20 Hz. Ultrasound used in medical imaging (sonography), cleaning, SONAR.

This question belongs to: Science Physics
Question #3 Report Error
A 2 kg object has potential energy 196 J at a height (g=9.8) of
A. 10 m
B. 98 m
C. 20 m
D. 196 m

Correct Answer: Option A


Explanation:
h = PE/(mg) = 196/(2×9.8) = 196/19.6 = 10 m.

This question belongs to: Science Physics