Question

Assertion: The frequency of violet colour of wavelength \(4000 \AA\) is \(7.5 \times 10^{14} \mathrm{~Hz}\). 

Reason: \(\mathrm{C}=v \lambda\)

\[\text{or } \nu = \frac{c}{\lambda}\]

\[= \frac{3 \times 10^{8}}{4000 \times 10^{-10}}\]

= 7.5 × 10¹⁴ Hz

Options

• If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.

• If both Assertion and Reason are true, but Reason is not correct explanation of the Assertion.

• If Assertion is true, but the Reason is false.

• If Assertion is false, but the Reason is true.

Answer 1

If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.

Explanation:

Using the wave formula $$c = \nu \lambda$$, the frequency is $$\nu = \frac{3 \times 10^8\text{ ms}^{-1}}{4000 \times 10^{-10}\text{ m}} = 7.5 \times 10^{14}\text{ Hz}$$.

Thus, the assertion is correct and directly justified by the reason.