Physics Answers

Natural magnesium occurs as a mixture of three isotopes: Mg 24 12 at 78,8%, Mg 25 12 at 10,1% and Mg 26 12 at 11,2%. Calculate the atomic mass of a natural sample of magnesium.

X-rays of wavelengths 1×10^-10 are scattered from a carbon block to undergo a 90° Campton scattering.

a) calculate the Campton shift

b) what is the kinetic energy of the recoiling electron

Using Bohr’s theory, calculate the energy required to remove the electron from the ground state of singly ionized helium, that is, helium with one electron already removed.

In the scattering of x-rays from a crystal of NaCl, it is assumed that the scattered x-rays undergo no change in wavelength. Show that this is a reasonable assumption by calculating the order of magnitude of the Compton wavelength for a sodium atom and a chlorine atom and comparing it with a typical x-ray wavelength of 0.10 nm.

How many photons per second are emitted by a 50-kW radio transmitter that operates at a frequency of 1200 kHz?

If the work function for a metal is 1.8 eV, what would be the stopping potential for light having a wavelength of 400 nm? (b) What would be the maximum velocity of the emitted photoelectrons at the metal’s surface? 

A source containing a mixture of hydrogen and deuterium atoms emits light containing two closely spaced red colors at  = 656,3 nm whose separation is 0.18 nm. Find the minimum number of lines needed in a diffraction grating, which can resolve these lines in the first order.

Two slits separated by 1.2 mm are placed 1.40 m from a screen. Light of wavelength 480 nm and 640 nm is incident on the slits. What is the separation distance on the screen of intensity maxima of the second order?

The barometer of a mountain hiker reads 750 mbars

at the beginning of a hiking trip and 650 mbars at the end.

Neglecting the effect of altitude on local gravitational acceleration,

determine the vertical distance climbed. Assume an

average air density of 1.20 kg/m3.

 A target in a shooting board consists of a vertical square wooden board, 0.250 m on a side and with a mass 0.750 g and pivots around a horizontal axis along its top edge. The board is stuck face-on at its center by a bullet of mass 1.90 g, travelling at 360 m/s that remains embedded in the board.

(a) (2 marks) What is the angular speed of the board just after the bullet’s impact?

(b) (2 marks) What maximum height does the center of the board reach from the equilibrium before it starts swinging down again?

(c) (2 marks) What minimum bullet speed is needed for the board to swing all the way over after the impact?