Explain how the eye and a camera differ in adjusting for a change in focus
What will be an ideal response?
The camera lens has a fixed focal length so it adjusts focus by varying the lens-film distance. The eye has an essentially fixed lens-retina distance so the focal length of the lens is varied by changing the lens curvature (by muscular action).
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A proton is moving at 
m/s and experiences a magnetic force of magnitude 
If the magnetic field makes an angle of 40
with respect to the velocity of the proton, what is the field's magnitude?
A. 
B. 
C. 
D. 
E. 
Compared to the Earth, the moon is no longer geologically active because
a. it is rotating too slowly. b. its radioactive elements were never abundant. c. it is much smaller in mass. d. its crust is too thin. e. it does not have water on its surface.
A quantity of an ideal gas is kept in a rigid container of constant volume. If the gas is originally at a temperature of 19°C, at what temperature will the pressure of the gas double from its original value?
A) 91°C B) 38°C C) 311°C D) 273°C E) 122°C
Bats can detect small objects such as insects that are of a size approximately that of one wavelength. If bats emit a chirp at a frequency of 50 kHz, and the speed of sound waves in air is 330 m/s, what is the smallest size insect they can detect?
a. 1.5 mm c. 5.5 mm b. 3.7 mm d. 6.6 mm