Question

Two statements are given one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer from the codes (A), (B), (C) and (D) as given below.
Assertion (A): X-rays are produced when slow moving electrons are stopped by a metal target of high atomic number.
Reason (R): X-rays consist of low-energy photons.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Both Assertion (A) and Reason (R) are false.

Hint:

X-rays are produced by high-energy electrons striking a metal target, and they consist of high-energy photons — not low-energy ones.

Answer 1

The Correct Option is D

Assertion (A) is false: X-rays are generated when electrons moving at high speed, not slow speed, impact a metal target with a high atomic number, such as tungsten. This rapid deceleration of electrons results in the emission of X-rays, a process called Bremsstrahlung. Consequently, the assertion of "slow moving electrons" is inaccurate. Reason (R) is also false: X-rays are high-energy photons, typically ranging from 1 keV to 100 keV or higher, significantly exceeding the energy of visible light. Therefore, describing them as "low-energy photons" is factually incorrect. As both statements are false, option (D) is the correct choice.