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
7
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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