If Venus (of radius R = 6050 km) absorbed all photons incident on it from the Sun, what magnitude of force would the solar radiation exert on Venus? Assume the effective wavelength of solar radiation is 550 nm and the solar luminosity is 3.78 x 1026 W. I know that Nhc/[tex]\lambda[/tex]=L where N is the number of photons being emitted and L is the luminosity. I also know F=Ndp/dt. where p is the momentum. p=h/[tex]\lambda[/tex] where h is planck's constant. Basically I solved for N using the first equations, but since Venus is smaller than the sun, it won't absorb all the photons the sun emits, only some. So I took the ratio between the radius of venus and the sun and multiplied it by n to get the percent of the photons incident to venus. I think used the wavelength they gave me to calculate p. Finally I took N(incident)xp=F. This however was wrong... Any ideas?