Chapter 21 Quiz
ÎWhich
of the following has nothing to do with EM waves?
‹ (a)
Dental x-rays
‹ (b) Radio broadcasting
‹ (c) Strumming a guitar
‹ (d) Cooking a microwave dinner
‹ (e) Responding with your HITT transmitter
PHY2054: Chapter 22
1
Chapter 21 Quiz
ÎA
grain of interplanetary dust is in the Sun’s gravitational
field. Ignoring all other influences, is it possible for the
grain to move away from the Sun?
‹ (a)
Yes, if the grain is sufficiently large
‹ (b) Yes, if the grain is sufficiently small
‹ (c) No, it cannot escape the Sun’s gravitational field
PHY2054: Chapter 22
2
Chapter 21 Quiz
ÎWhich
statement is true? The energy carried by an
electromagnetic wave in a vacuum
‹ (a)
propagates at the speed of light
‹ (b) consists of only electric field contributions
‹ (c) propagates along the direction of the electric field
‹ (d) consists of E and B fields pointing in the same direction
‹ (e) none of the above
PHY2054: Chapter 22
3
Chapter 22: Reflection
ÎLaw
of reflection
‹ Incident
‹
θ1′ = θ1
ray, reflected ray, normal lie in one plane
PHY2054: Chapter 22
4
Reflection Law Applies to non-Flat Surfaces
θ
θ′
PHY2054: Chapter 22
5
Chapter 22: Refraction
ÎIndex
of refraction n and speed of light in medium
c
v=
n
ÎLaw
of refraction (Snell’s law)
‹ Incident
ray, refracted ray,
normal lie in one plane
‹ n1 sin θ1
= n2 sin θ 2
n1
n2
PHY2054: Chapter 22
6
Refraction at Air-Water Interface
sin θ1
sin θ 2 =
1.333
θ1
θ2
n1 = 1.000
θ1
θ2
0°
0°
n2 = 1.333
15°
11.2°
30°
22.0°
45°
32.0°
60°
40.5°
75°
46.4°
90°
48.6°
n1 sin θ1 = n2 sin θ 2
Critical angle (more later)
PHY2054: Chapter 22
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Following Reflected and Refracted Rays
ÎRay
1 is the incident ray
ÎRay
2 is the reflected ray
ÎRay
3 is refracted into
the lucite
ÎRay
4 is reflected in the
lucite
ÎRay
5 is refracted as it
enters the air from the
lucite
PHY2054: Chapter 22
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