# User talk:Guy vandegrift/Permanent essay by Work Study Student

## Test 4 phy1120 spring 2015

1

Shown is a corrective lens by a person who needs glasses. This ray diagram illustrates

 a) how a farsighted person might see a distant object b) how a nearsighted person might see a distant object c) how a farsighted person might see an object that is too close for comfort d) how a nearsighted person might see an object that is too close for comfort

2

An important principle that allows fiber optics to work is

 a) the Doppler shift b) total external refraction c) total internal reflection d) the invariance of the speed of light e) partial internal absorption

3

In optics, normal means

 a) parallel to the surface b) to the left of the optical axis c) to the right of the optical axis d) perpendicular to the surface

4

The law of reflection applies to

 a) only light in a vacuum b) flat surfaces c) curved surfaces d) telescopes but not microscopes e) both flat and curved surfaces

5

Shown is a corrective lens by a person who needs glasses. This ray diagram illustrates

 a) how a nearsighted person might see an object that is too close for comfort b) how a farsighted person might see a distant object c) how a nearsighted person might see a distant object d) how a farsighted person might see an object that is too close for comfort

6

When light passes from air to glass

 a) it bends away from the normal b) the frequency decreases c) the frequency increases d) it bends towards the normal e) it does not bend

7

After passing through a the lens of a camera or the eye, the focal point is defined as where the rays meet.

 true false

8

Mr. Smith is gazing at something as shown in the figure to the left. Suppose he does not refocus, but attempts to stare at the star shown in the figures below. Which diagram depicts how the rays from the star would travel if he does not refocus?

9

The focal point is where

 a) rays meet whenever they pass through a lens b) rays meet whenever they are forming an image c) rays meet if they were parallel to the optical axis before striking a lens d) rays meet if they are parallel to each other e) the center of the lens

10

When light passes from glass to air

 a) it bends away from the normal b) the frequency increases c) the frequency decreases d) it bends towards the normal e) it does not bend

11

Which lens has the shorter focal length?

 They have the same focal lengh.

12

If this represents the eye looking at an object, where is this object?

 One focal length in front of the eye Two (of the other answers) are true very far away at infinity directly in front of the eye (almost touching)

13

A cosmic ray alpha particle encounters Earth's magnetic field at right angles to a field of 23.7 μT. The kinetic energy is 438 keV. What is the radius of particle's orbit?

 a) 4 x 103 m. b) 1.3 x 104 m. c) 4 x 104 m. d) 1.3 x 105 m. e) 4 x 105 m.

14

Two parallel wires are 7.3 meters long and are separated by 6.7 mm. What is the force if both wires carry a current of 9.3 amps?

 a) 1.88 x 10-3 newtons b) 5.96 x 10-3 newtons c) 1.88 x 10-2 newtons d) 5.96 x 10-2 newtons e) 1.88 x 10-1 newtons

15

Blood is flowing at an average rate of 16.5 cm/s in an artery that has an inner diameter of 4.7 mm. What is the voltage across a hall probe placed across the inner diameter of the artery if the perpendicular magnetic field is 0.15 Tesla?

 a) 1.16 x 10-5 Volts b) 3.68 x 10-5 Volts c) 1.16 x 10-4 Volts d) 3.68 x 10-4 Volts e) 1.16 x 10-3 Volts

16

An electron tube on Earth's surface is oriented horizontally towards magnetic north. The electron is traveling at 0.06c, and Earth's magnetic field makes an angle of 45.5 degrees with respect to the horizontal. To counter the magnetic force, a voltage is applied between two large parallel plates that are 45 mm apart. What must be the applied voltage if the magnetic field is 36μT?

 a) 2.1 x 100 volts b) 6.6 x 100 volts c) 2.1 x 101 volts d) 6.6 x 101 volts e) 2.1 x 102 volts

17

Two orbiting satellites are orbiting at a speed of 58 km/s perpendicular to a magnetic field of 46 μT. They are connected by a cable that is 22 km long. A voltmeter is attached between a satellite and one end of the cable. The voltmeter's internal impedance far exceeds the net resistance through the ionosphere that completes the circuit. What is the measured voltage?

 a) 2.72 x 104 volts. b) 3.3 x 104 volts. c) 4 x 104 volts. d) 4.84 x 104 volts. e) 5.87 x 104 volts.

18

Referring to the previous question, the voltmeter is replaced with by a 45.8 kΩ resistor, causing the the voltage falls to 78% its original value. What is the effective internal impedance of the ionospheric plasma?

 a) 8.801 x 100 kΩ b) 1.066 x 101 kΩ c) 1.292 x 101 kΩ d) 1.565 x 101 kΩ e) 1.896 x 101 kΩ

19

Referring to the previous problem, what power is developed by the 45.8 kΩ resistor?

 a) 3.12 x 104 Watts b) 3.78 x 104 Watts c) 4.57 x 104 Watts d) 5.54 x 104 Watts e) 6.71 x 104 Watts

20

An loop of wire with 31 turns has a radius of 0.9 meters, and is oriented with its axis parallel to a magetic field of 0.83 Tesla. What is the induced voltage if this field is reduced to 35% of its original value in 1.7 seconds?

 a) 2.07 x 101 volts b) 2.5 x 101 volts c) 3.03 x 101 volts d) 3.67 x 101 volts e) 4.45 x 101 volts