Physics Answers

Two sinusoidal waves travel in the same direction with the same amplitude, wavelength, and speed. Their resultant wave function is given by: y(x,t) = Ares sin(kx-ωt+π/4). If Ares = 8 cm, then the amplitude, A, of each of the original sinusoidal waves producing this resultant wave is:

Consider two identical waves travelling in the positive x-direction. The two waves start at the same position but at different times, t1 and t2. What should the time difference ∆t be in order to have a phase difference of π/4. Assume that the frequency of each wave is f = 20 Hz.

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?

Interstellar space far from any star is filled with atomic hydrogen at a density of 1atom/cm at a very low temperature of 273k find

(a) the pressure of the interstellar gas

(b) the root mean speed of the atoms

(c) the edge length of a cube that will contain atoms with a total energy of one joule

Two waves travelling in the same direction are given by: y1(x,t) = 0.2 sin⁡(3πx-20t+π/2) and y2(x,t) = 0.2 sin⁡(3πx-20t), where x and y are in meters and t is in seconds. The wave function of the resultant wave is:

While conducting a photoelectric-effect experiment with light of a certain

frequency, you find that a reverse potential difference of 1.25 V is required

to reduce the current to zero. Find (a) the maximum kinetic energy and (b)

the maximum speed of the emitted photoelectrons.

Find the minimum magnetic field needed for the Zeeman effect to be observed

in a spectral line of 400 nm wavelength when a spectrometer whose resolution

is 0.01nm is used.

One of the most prominent spectral lines of Calcium is the one with

wavelength 𝜆 = 4226.73 𝐴

𝑜

[transition from 𝑝(𝑙 = 1) to 𝑠(𝑙 = 0)]. Calcium

atoms exhibit normal Zeeman patterns when placed in a uniform magnetic

field of 4 𝑇𝑒𝑠𝑙𝑎. Calculate the wavelength of the three components of a

normal Zeeman pattern and the separation between them.

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?