John's face is 20 cm in front of a concave shaving mirror of focal length 30 cm. How large an image does he observe?
A) half as large as his face
B) of the same size as his face
C) twice as large as his face
D) three times as large as his face
E) four times as large as his face
D
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The planet Mars reaches its closest point to the Earth approximately every
A) 26 months B) 12 months C) 6 months D) 36 months
In our solar system, Jovian planets are
A) large, made mostly of gases and liquids with low densities, and found far from the Sun B) small, made of pure rock with high densities, and found close to the Sun C) large, made of pure gases with low densities, and found far from the Sun D) small, made mostly of rock and iron with high densities, and found close to the Sun
Refraction occurs at the interface between two transparent media because:
1.The mass density of the material changes. 2.The frequency of the light changes. 3.The speed of light is different in the two media. 4.The direction of the light changes. 5.Some of the light is reflected. 6.None of the above.
Suppose two flat glass plates 30-cm long are in contact along one end and separated by a human hair at the other end. If the diameter of the hair is 50 ?m, find the separation of the interference fringes when the plates are illuminated by green light, ? = 546 nm