The human eye can just detect green light of wavelength 500. nm, which arrives at the retina at the rate of 2 10-18 W. How many photons arrive each second?
What will be an ideal response?
Question 2
The Earth's magnetosphere is a
A) sphere of magnetism found just outside the molten outer core of the Earth
B) spherical magnetic field generated by magnetic rocks on the Earth's surface
C) cavity carved out in the solar wind by the Earth's magnetic field
D) sphere of magnetism caused by the motion of charged particles in the Earth's outer atmosphere
Question 3
A planet of constant mass orbits the sun in an elliptical orbit. Neglecting any friction effects, what happens to the planet's rotational kinetic energy about the sun's center?
A) It decreases continually.
B) It increases continually.
C) It remains constant.
D) It increases when the planet approaches the sun, and decreases when it moves farther away.
E) It decreases when the planet approaches the sun, and increases when it moves farther away.
Question 4
If you place a plane mirror vertically into water, and a dolphin moves toward it with a speed of 4 m/s, she will see her image move toward her at a relative speed of
A) 6. m/s.
B) 10. m/s.
C) 2. m/s.
D) 4. m/s.
E) 8. m/s.