What is a photon?

If $5\%$ of the energy supplied to a bulb is irradiated 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 Compton effect supports the fact that

Write the value and unit of Planck's constant.

$A$ proton moving with a momentum $p_{1}$ has a kinetic energy $1/8$th of its rest mass-energy. Another light photon having energy equal to the kinetic energy of the proton possesses a momentum $p_{2}$. Then,the ratio $\frac{p_{1}-p_{2}}{p_{1}}$ is equal to

The value of Planck's constant is