Photons of wavelength A are incident on a metal. The most energetic electrons ejected from the metal are bent into a circular arc of radius R by a magnetic field having a magnitude B. What is the work function of the metal?

The Earth has an average surface temperature of 288K and the Sun has an average surface temperature of 5800K. Assume them to be black bodies. If the only radiation that either black body emitted was at it's peak wavelength how many more photons would Earth need to radiation than receive in order for the climate to be stable.

One of the first signs of sunburn is the reddening of the skin (called erythema). As a very rough rule of thumb, erythema occurs if 14.0 mJ of ultraviolet light of approximately 308 nm wavelength (referred to as UVB radiation) is incident on the skin per square centimeter during a single exposure. How many photons are incident on 1.00 cm2 of skin in this amount of exposure? photons

Suppose a linear accelerator (linac) creates a X-ray beam where every individual photon has an energy of 19 MeV. If 3x1010 photons are produced over 90x10-15 s, as measured through an area of 3.1 m², determine the intensity of the X-ray beam. I = B W/m²