1. Two pieces of optically flat glass (n=1.5) touch at one edge and a separated

Question

1. Two pieces of optically flat glass (n=1.5) touch at one edge and a separated by a thin stretched fiber at the opposite edge. Light of wavelength 500 nm is shone from above and 100 dark fringes are counted. How thick is the fiber?

a) 25 um

b) 13 um

c) 5 um

d) 100 um

e) 50 um

2. An ideal gas constant volume gas thermometer has pressure 2 atm at the triple point of water. What is the temperature when the pressure in the thermomter is 6 atm?

a) 548 K

B) 410 K

C) 683 K

D) 137 K

E) 819 K

3. In a Hall experiment a conducting strip of thickness d=100 um is placed in a magnetic field B= .05 T. The magnetic field is perpendicular to the direction of the strip along which there is a 10 A current. What is the Hall voltage measured across the strip if the charge carrier density is 2.5 *10^28 /m^3 in this material?

A) 6.2 %u03BCV B) 1.3 %u03BCV C) 4.2 %u03BCV D) 2.5 %u03BCV E) 0.72 %u03BCV

MUST SHOW WORK FOR POINTS

Explanation / Answer

1)

ans:d. 100 um

m=600

2nt = (m+0.5)(lambda)

2*1.5*t= (600+0.5)*500*10^-9

solving

t= 100*10^-6m

=100 um

2)

2/273 = 6/x

x= 273 * 3 = 819 K

3)

1.3v

Vh=IB/ned
where I is the current across the plate length, B is the magnetic field, d is the depth (thickness) of the plate, e is the elementary charge, and n is the charge carrier density of the carrier electrons.

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