A compound lens is made by joining the plane surfaces of two thin plano-convex lenses of different glasses
The radius of curvature of each convex surface is 80 cm. The indices of refraction of the two glasses are 1.50 and 1.60. What is the focal length of the compound lens?
A) 67
B) 69
C) 71
D) 73
E) 75
Answer: D
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Consider a long thin straight wire with a current I. Which of the following statements about the magnetic field lines is true?
A. Field lines are parallel to the wire.
B. Field lines are perpendicular to the wire.
C. Field lines are directed radially away from the wire.
D. Field lines are circles centered on any point on the wire.
A silicon rod 20 cm in diameter and 30 cm long is exposed to a high temperature at one end so that the end is at 400ºC whereas the remaining surfaces are at 60ºC. Estimate the centerline temperature distribution through the rod.
What will be an ideal response?
In which part of the Sun are gamma rays produced?
a) corona b) core c) chromosphere d) convection zone e) photosphere
Bar A has one end painted green and the other end red and may or may not be a magnet. A student brings the north pole of a bar magnet M close to the green end of A. He observes that the green end is attracted. He can conclude that
A. A is a magnet and the green end is a south pole. B. A might be a magnet; this observation does not provide enough information to determine whether or not it is. C. A is a magnet and the green end is a north pole. D. A is not a magnet.