Question

If $n_r$ and $n_b$ are respectively, the number of photons emitted by a red bulb and a blue of equal power in a given time, then

• A. $n_r=n_b$
• B. $n_r<n_b$
• C. $n_r>n_b$
• D. nothing can be predicated

Answer 1

Answer: (C)

$n_r>n_b$

Since, $P_r=P_b$

$r$ for red and $b$ for blue.

$P_r=P_b$

or, $n_r\times \frac{hc}{{\lambda }_r}=n_b\times \frac{hc}{{\lambda }_b}$

or, $\frac{n_r}{n_b}=\frac{{\lambda }_r}{{\lambda }_b}$

Since, wavelength of red bulb in greater than the wavelength of blue bulb.

or, $n_r>n_b$.