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 produced when high-speed (not slow) electrons strike a metal target (like tungsten) with a high atomic number. The sudden deceleration of these electrons leads to emission of X-rays, a phenomenon known as Bremsstrahlung or braking radiation. Therefore, the statement about "slow moving electrons" is incorrect. Reason (R) is also false: X-rays are high-energy photons, with energies typically in the range of 1 keV to 100 keV or more. They lie well above the visible spectrum in terms of energy. Hence, calling them "low-energy photons" is factually wrong. Since both statements are incorrect, the correct answer is option (D).