HOMEWORK 1

K6005

(PHY112)

1.Consider a black-body of surface area 25.0 mm2 and temperature 7500K (a)How much power does

it radiate?(b)At what wavelength does it radiate most intensely? Find the spectral power per

wavelength at (c) this wavelength and at wavelength of (d) 1nm (e) 5nm (UV light or an x-ray ) (f)

400nm(g) .01 micrometer?

2. A metal has threshold frequency of > 7 X 1014 Hz. A source emitting radiation of 7 X 1014 Hz is given

a velocity towards the metal to eject photoelectrons from the metal. (a) Explain how this procedure

can produce photo electrons (b) when the speed of the light source is equal to .280c ,photoelectrons

just begin to be ejected from the metal? What is the work-function of the metal? (c) When the

speed of the light source is increased to .900c, determine the maximum kinetic energy of the

photoelectrons.

3. A free electron at rest is scattered by a photon having energy E so that the angle of scattering of

electron is equal to that of the scattered photon. What is the angle of scattering for electron and

photon? With what energy and momentum is the photon scattered? What is the Kinetic energy and

momentum of the scattered electron?

PART-B

4. A pair of slits having a 1.00 mm separation is placed in the path of a beam of neutrons travelling

at 0.400m/s. Detectors are placed at a distance of 10.0m from the slits.(a) When the neutron

reaches the detector can we say which slit the neutron has passed through? (b) What is the De-

Broglie wavelength of the neutrons(c) How far off axis is the first zero-intensity point of the detector.

5. An electron and a bullet (m=0.020 Kg) have the velocity 500 m/s, accurate within 0.010%.Within

what limits could we determine the position of the objects along the path of the beam.

6. A metal having work function 3.44 eV is illuminated normally with ultraviolet light with a single

wavelength and intensity 550 W/m2. The maximum speed of the photoelectrons is 420 km/s. (a) Find

the maximum possible rate of photoelectron emission from 1 cm2 of the surface assuming that each

photon produces one photoelectron. (b) Find the electric current due to photoelectrons.(c) Compare

the maximum possible current with the actual current.