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

The number of photons emitted per second by a bulb of $66 \ W$ power emitting waves of wavelength $600 \ nm$ is . . . . . . . $(h = 6.6 \times 10^{-34} \ J \cdot s)$

The frequency of a photon having energy $66 \ eV$ is:

$A$ light bulb emits $5\%$ of its energy as visible light. How many quanta are emitted per second by a $100 \ W$ lamp? (Assume the wavelength of visible light is $5.6 \times 10^{-5} \ cm$)

The frequency of a photon having energy $100 \ eV$ is $(h = 6.6 \times 10^{-34} \ J \cdot s)$.

$A$ photon and an electron, each of $20 \text{ eV}$ energy, move in free space. The ratio of linear momentum of electron $p_e$ to that of photon $p_{ph}$ is : (Take speed of light = $3 \times 10^8 \text{ ms}^{-1}$, charge of electron = $-1.6 \times 10^{-19} \text{ C}$ and mass of electron = $9 \times 10^{-31} \text{ kg}$)