Atomic and Nuclear Physics Answers

The Earth may be considered to be a uniform sphere of radius 6.38 × 106 m. Its mass is assumed to be concentrated at its centre.

Given that the gravitational field strength at the Earth’s surface is 9.81 N kg–1, show that the mass of the Earth is 5.99 × 1024 kg.

What is the force between two protons that are separated by 1.0 mm? The charge of a proton is 1.6 × 10^-19 C.

The Q value of the Na23 (n,α) F20 reaction is -5.4MeV. Determine the threshold energy of the neutrons for this reaction (22.9898u, 18.9964u, 4.0039u, 1.008665u are the masses of Na23, F20 α and n respectively).

How many grams of an unknown gas having a molecular weight of 24.34 g/mol will be produced at STP?

Two equal charges are separated 75cm apart in free air. Calculate the quantity of either charge if the force between them is 0.17N. What will be the quantity if the charges are situated in an insulating medium of dielectric constant 10?

Derive the expression of the Q = ΔE of a nuclear reaction, hence, determine the Q value and the nature of the reaction F19 (H1,α) O16( 18.998405u, 15.994915u, 4.002603u, 1.007825u are masses of F19, O16, α, H1) respectively.

a ii). Discuss the primary processes by which gamma rays interact with matter

b). The Q value of the Na23 (n,α) F20 reaction is -5.4MeV. Determine the threshold energy of the neutrons for this reaction (22.9898u, 18.9964u, 4.0039u, 1.008665u are the masses of Na23, F20 α and n respectively).

Charge q1 = 7.00 μC is at the origin, and charge q2 = -5.00 μC is on the x-axis, 0.300 m from the origin as shown below. (a) Find the magnitude and direction of the electric field at point P, which has coordinates (0, 0.400) m. (b) Find the force on a charge of 2.00 × 10-8 C placed at P

Problem - A sample of gallium arsenide (GaAs) is doped with 1010 silicon atoms per cm3

.

Ninety-five percent of the silicon atoms replace arsenic atoms and the remaining five percent

replace gallium atoms. T = 300 K. The intrinsic carrier concentration, ni

, is equal to 9 × 106 cm3

.

Calculate the electron and hole concentration as well as the position of the Fermi level.

Problem – A silicon wafer is doped with 2×1016 boron and 1016 phosphorus atoms per cm3

.

Calculate n, p, and EF at room temperature assuming complete ionization. Repeat the same for 8

x 1015 boron atoms per cm3

and 1016 phosphorus atoms per cm3

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Problem-The intrinsic temperature of a semiconductor is the temperatures at which the intrinsic

carrier concentration equals the impurity concentration. Find the intrinsic temperature for a

silicon sample doped with 1015 phosphorus atoms/cm3

.