$A$ source $S_1$ is producing $10^{15}$ photons per second of wavelength $5000 \; \mathring{A}$. Another source $S_2$ is producing $1.02 \times 10^{15}$ photons per second of wavelength $5100 \; \mathring{A}$. Then,$(\text{power of } S_2) / (\text{power of } S_1)$ is equal to

$A$ photon,an electron,and a uranium nucleus all have the same wavelength. The one with the most energy is:

$A$ laser produces a beam of light of frequency $5 \times 10^{14} \,Hz$ with an output power of $33 \,mW$. The average number of photons emitted by the laser per second is (Planck's constant $h = 6.6 \times 10^{-34} \,J \,s$)

In an accelerator experiment on high-energy collisions of electrons with positrons,a certain event is interpreted as annihilation of an electron-positron pair of total energy $10.2 \; BeV$ into two $\gamma$-rays of equal energy. What is the wavelength associated with each $\gamma$-ray? $(1 \; BeV = 10^9 \; eV)$

$A$ bulb has a power of $60 \, mW$ and emits light of wavelength $6000 \, \mathring{A}$. Calculate the number of photons emitted by the bulb per second.

Consider a hypothetical annihilation of a stationary electron with a stationary positron. What is the wavelength of the resulting radiation? ($h =$ Planck's constant,$c =$ speed of light,$m_0 =$ rest mass)