Which of the following has a mass closest in value to that of the positron? $(1\;a.m.u = 931\;MeV)$

$A$ bulb lamp emits light of mean wavelength of $4500 \mathring A$. The lamp is rated at $150 \text{ W}$ and $8 \%$ of the energy appears as emitted light. How many photons are emitted by the lamp per second?

Monochromatic light of wavelength $667 \, nm$ is produced by a helium-neon laser. The power emitted is $9 \, mW$. The number of photons arriving per second on average at a target irradiated by this beam is:

If $E$ and $P$ are the energy and the momentum of a photon respectively,then on reducing the wavelength of the photon:

The radiation with frequency $1.0 \times 10^{14} \ Hz$ lies in the infrared region. The energy of one photon of this radiation in joules is:

Write the equation for the energy of a photon.