Question

If $n_r$ and $n_b$ be respectively the number of photons emitted by a red bulb and a blue bulb of equal power in one second, then $n_r$ is $n_b.$

• A. equal to
• B. less than
• C. greater than

Answer 1

The correct option is C greater than

Let $v_r$ and $v_b$ be the freqencies of red and blue light respectively. We know that $v_b>v_r$.

Now, since the two sources emit with equal power, the energy emitted per second will be -

$n_r\left(h{v}_r\right)=n_b\left(h{v}_b\right),$

which would imply,

$n_r{v}_r=n_b{v}_b.$

Since $v_b>v_r$, we can directly conclude: $n_r>n_b$.