An optical system comprises in turn, from left to right: an observer, a lens of focal length +30 cm, an erect object 20 mm high, and a convex mirror of radius 80 cm
The object is between the lens and the mirror, 20 cm from the lens and 50 cm from the mirror. The observer views the image that is formed first by reflection and then by refraction. What is the position of the final image, measured from the mirror?
A) 90 cm
B) 102 cm
C) 114 cm
D) 126 cm
E) 138 cm
Answer: C
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Consider two less-than-desirable options. In the first you are driving 30 mph and crash head-on into an identical car also going 30 mph
In the second option you are driving 30 mph and crash head-on into a stationary brick wall. In neither case does your car bounce off the thing it hits, and the collision time is the same in both cases. Which of these two situations would result in the greatest impact force? A) hitting the brick wall B) hitting the other car C) The force would be the same in both cases. D) We cannot answer this question without more information. E) None of these is true.
The potential difference across the terminals of a storage battery not connected in any circuit is observed to be 12 V. When it is connected to an external resistance the potential difference across the terminals is observed to be 11 V while the current in the external resistance is 3 A. What is the internal resistance of the battery?
A. 2.0 ohms B. 0.33 ohm C. 5.5 ohms D. 1.0 ohm E. Zero ohms
Which of the following is not one of the Bohr postulates?
1.The laws of classical physics apply to orbital motion of the electrons but not during transitions from one orbit to another. 2.The possible energies that the electron can have are discrete and depend on the orbit radius. 3.Electrons emit electromagnetic radiation only during transitions between orbits and not while in an allowed orbit. 4.Permissible orbits have an angular momentum which is an integer multiple of h/2?. 5.The frequency of the radiation emitted during a transition is related to the energy difference between the orbits by f = ?E/h.
In an RLC series circuit, if the AC frequency is decreased to a very small value, what value does the phase angle between the current and voltage approach?
a. 90° b. 0° c. –90° d. 45°