3. A
When the wave enters the glass, its frequency does not change; otherwise, its
color would change. However, the wave moves at a different speed, since the
speed of light, v, in different
substances is given by the formula v = c/n,
where c is the speed of light in a
vacuum, and n is the index of
refraction for the given substance. Since
?glass = v/ƒ,
we can also reason that
?glass = c/nƒ .
Further, we know that
c/n = ?air,
so substituting these equations in, we get:
4. C
Statement I is true, but it doesn’t explain why a refracted ray should have a
different wavelength. The fact that some of the incident ray is reflected means
that the refracted ray will have a different amplitude, but it will not affect
the frequency.
Statement II is false, and even if it were true, a change in energy would affect
the frequency of the wave, not its wavelength.
Statement III correctly explains why refracted rays have different wavelengths
from their incident rays. A light ray will maintain the same frequency, and
hence color, when it is refracted. However, since the speed of light differs in
different substances, and since the wavelength is related to the speed of light,
v, by the formula
? = v/ƒ ,
a change in the speed of light will mean a change in the wavelength as well.
5. A
Snell’s Law gives us the relationship between the indices of refraction and the
angles of refraction of two different substances:
n1
sin?1
=
n2
sin?2.
We know that
n1,
the index of refraction for air, is 1, and
we know that
n2,
the index of refraction for plastic, is 2.
That means we can solve for sin?2:
6. B
Total internal reflection occurs when the refracted ray is at an angle of
9?° or greater, so that, effectively, the
refracted ray doesn’t escape into the air. If
?1
= 9?°, then sin?1
= 1, so by Snell’s Law:
?2 = sin-1 1/2
7. E
Only concave mirrors and convex lenses can produce images that appear upside
down. However, concave mirrors produce these images on the same side of the
mirror as the object, while convex lenses produce these images on the opposite
side of the mirror from the object.
8. E
Whenever we see a pattern of maxima and minima, we know we are dealing with the
phenomenon of diffraction, which rules out the possibility thatA is a polarization filter or a prism.
Both single- and multiple-slit diffraction gratings tend to produce bands of
light, but not concentric circles. The correct answer is E, the pinhole:
light passing through the pinhole will spread out in concentric circles and will
alternate between bright and dark patches to produce concentric rings.
9. D
Visible light can be polarized because it travels as a transverse wave, meaning
that it oscillates perpendicular to the direction of its motion. Polarization
affects the oscillation of transverse waves by forcing them to oscillate in one
particular direction perpendicular to their motion. Sound waves, on the other
hand, are longitudinal, meaning that they oscillate parallel to the direction of
their motion. Since there is no component of a sound wave’s oscillation that is
perpendicular to its motion, sound waves cannot be polarized.
10. A
The idea behind polarized sunglasses is to eliminate the glare. If the solar
glare is all at a 9?° angle to the normal
line, sunglasses polarized at a ?° angle to
this normal will not allow any of the glare to pass. Most other light is not
polarized, so it will still be possible to see the road and other cars, but the
distracting glare will cease to be a problem.
Back
Next
div>
Next to display next topic in the chapter.
Practice Questions
Video Lessons and 10 Fully Explained Grand Tests
Large number of solved practice MCQ with explanations. Video Lessons and 10 Fully explained Grand/Full Tests.