Atomic and Nuclear Physics Answers

Using the concept of QM you have learned (application of the SE

to H-like atoms), derive / discuss the (existence of ) quantum

numbers n, l, ml

A large number of neon atoms are in thermal equilibrium. What is the ratio

of the number of atoms in a 5s state to number in 3p state at (a) 300K; (b)

600K; (c) 1200K? The energy difference between two states is 1.96 eV. (d) at

any of these temperatures, the rate at which a neon gas spontaneously emits

632.8nm radiation is quite low. Explain why?

On 20 July 1969, the astronauts of Apollo 11 placed a reflector on the surface

of the moon that with the telescope and electronic equipment on earth allows

measurements of the time of flight of laser pulses from earth to the moon and

back. Scientists are able to measure the time of flight of laser pulse from earth

to the moon and back with an accuracy of one nanosecond. What is the

accuracy of the distance to the moon distance?

X-ray from a certain cobalt target tube are composed of the strong 𝐾 series

of Cobalt and weak 𝐾 lines due to impurities. The wavelengths of 𝐾𝛼 are

1.785𝐴

𝑜

for Cobalt and 2.285𝐴

𝑜

and 1.537𝐴

𝑜

for impurities. (a) What

elements are they? [For the 𝐾-series, a=1 in Moseley’s law]

The doctor measured the count rate from the sample. the count rate was 80 seconds per second.

half life of radium-226 = 1600years

calculate the count rate in 6400 years

Describe the mode of operation of one instrument which uses the radiation heat transfer

mechanism

13.Electron are accelerated in a television tube through a potential difference of 9.8kV. Find the highest frequency and minimum wavelength of the electromagnetic wave emitted, when these strike the screen of the tube. In which region of the spectrum will these lie? a. Differentiate X-rays and visible light in terms of the origin of these EM radiations. b. What voltage must be applied to an X-ray tube for it to emit X-rays with minimum wavelength 0.5 A˚ ?

Find the kinetic, potential, and total energies of the hydrogen atom in the first excited level, and find the wavelength of the photon emitted in the transition from the first excited level to the ground level.

.Find the yield and estimate the average cross section for the (a, n) reaction excited by 7 MeV a-particles in a thick aluminum target if 1.60 × 109 neutrons are emitted per second. The a-particle current is 1.56 1014 s-1

(A) Explain how pure metal and a semi conductor can be distinguished through the effect of temperature on their electrical resistance

(B) explain what is meant by (I) an n-semi conductor (ii) a p-semiconductor

(C) state two advantages and one disadvantage of a junction diode over a thermionic valve