Vision Problems: What power contact lens should be used to correct the vision of a farsighted person whose near point is 80 cm so she can see things clearly that are 25 cm in front of her?
A. +2.8 diopters
B. -2.8 diopters
C. -4.0 diopters
D. -4.2 diopters
E. +4.2 diopters
Answer: A
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The term "cosmic distance ladder" refers to the fact(s) that:
Select the ones that apply: a. change in apparent position of object on sky through Earths orbit, which gives a measure of distance. (p=1/D) b. Spectral classification of star, which gives luminosity.D*=Sq rt L/4pieB c. variable stars whose luminosity is related to their period.D*=Sq rt L/4pieB d. relation between a galaxy's rotation rate and luminosity. D*=Sq Rt Lg/4pieBg e. Exploding star whose luminosity can be determined by its light curve. Dg=SqRt Lsn/4pieBsn f. Relation between galaxies recession velocity and distance.D=V/H g. All of the above facts.
The energy required to accelerate an interstellar spaceship depends on
A) its mass only B) its final velocity only C) the type of fuel it uses D) its mass and final velocity
A merry-go-round, having a radius of 2.5 m, is set in motion starting from rest, by students applying a force of 500 N tangential to the rim of the wheel. After five seconds of torque, the students let go and measure the rotational speed: 1.25 rad/s. The rotational inertia of the merry-go-round is
A. 5.0 × 103 kg m2. B. 1.7 × 103 kg m2. C. 1.0 × 104 kg m2. D. 2.5 × 103 kg m2. E. 7.5 × 102 kg m2.
When you look through a sheer curtain at a distant street lamp, you see a pattern of colored spots of light. This occurs by
a. polarization of light in scattering and partial absorption by the threads. b. interference of light waves that pass through the threads with light waves that pass through the openings between the threads. c. refraction of light waves differentially in the cylindrical threads. d. diffraction of light waves passing through the two dimensional pattern of openings between the threads. e. reflection of light waves by the sides of the threads.