Consider a thin target `(10^-2m square, 10^-3 m thickness)`of sodium, which produces a photocurrent of `100muA` when a light of intensity `100W/m^2(lambda=660nm)` falls on it. Find the probability that a photoelectron is produced when a photon strikes a sodium atom.`[Take density of Na=0.97 kg/m^3]`.

A ball is thrown upwards from the top of a tower 40 m high with a velocity of 10 m/s. Find the time when it strikes the ground. Take g=10 m//s^2.

The electromagnetic waves of intensity 4.5 xx 10^(-3) W m^(-2) fall on a surface and are completely absobed.Find teh pressure exerted by the radiation.

Radiation of wavelength 5000 oversetcircA and of intensity 2xx10^-3w cm^-2 falls on a photosensitive surface. Assuming that every absorbed photon results in the ejection of photoelectron, find how many photoelectrons are produced per cm^2 per sec.

Three polaroids are placed insuch a manner that the third polaroid is crossed with the first.When a beam of unpolarised light of intenstiy 24 W m^(-2) falls on the first polaroid,the intensity of light reduces to 3W m^(-2) on emerging fromo the thrid polariod.Find the angle between the trnasmission axes of the second and third polaroid.

Two thin lenses,when in contact,produce a combinatin of power+10 dioptres.When they are 0.25 m apart,the power reduces to +6 dipotres.Find the power of the two lenses.

If a man lifts a load up with the help of rope such that it raises the load of mass 50 kg to a height of 20 m in 100 seconds. Find the power of man. (Take g = 10ms^-2 )

The energy flux of sunlight reaching the surface of the earth is 1.388 xx 10^3 W/m^2 . How many photons per square metre are incident on the Earth per second? Assume that the photons in the sunlight have an average wavelength of 550 nm.

Find out the resistivity of a conductor in which a current density 2.5 xx 10^6 A m^-2 is found to exist, when an electric field of 15 V m^-1 is applied on it.

In a photoelectric effect set up, a point source of light of power 3.2 xx10^(-3) W emits monoenergetic photons of energy 5eV.The source is located at a distance of a stationary metallic sphere of work function 3eV and radius 8xx10^(-3)m .The efficiency of photoelectron emission is one for every 10^(6) incident photons.Assume that the sphere is isolated and initially neutral and the photoelectrons are initially swept away after emission. Find the ratio of the wavelength of incident light to the de Broglie wavelength of the fastest phtotelectrons emitted.