At what rate does a star emit photons? For simplicity, assume that the star's entire emission at the rate of 4.6 x 1029 W is at the single wavelength of 550 nm. Number i 1045 Units A sodium lamp emits light at the power P = 100 W and at the wavelength/l = 563 nm, and the emission is uniformly in all directions. (a) At what rate are photons emitted by the lamp? (b) At what distance from the lamp will a totally absorbing screen absorb photons at the rate of 1.00 photon /cm2s? (c) What is the rate per square meter at which photons are intercepted by a screen at a distance of 2.50 m from the lamp? (a) Number n Units v (b) Number n Units v (c) Number n Units v The stopping potential for electrons emitted from a surface illuminated by light of wavelength 489 nm is 0.670 V. When the incident wavelength is changed to a new value, the stopping potential is 1.42 V. (a) What is this new wavelength? (b) What is the work function for the surface? (a) Number Units v (b) Number n Units v