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0. Math Review31m
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1. Intro to Physics Units1h 29m
2. 1D Motion / Kinematics3h 56m
3. Vectors2h 43m
4. 2D Kinematics1h 42m
5. Projectile Motion3h 6m
6. Intro to Forces (Dynamics)3h 22m
7. Friction, Inclines, Systems2h 44m
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9. Work & Energy1h 59m
10. Conservation of Energy2h 54m
11. Momentum & Impulse3h 40m
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17. Periodic Motion2h 9m
18. Waves & Sound3h 40m
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20. Heat and Temperature3h 7m
21. Kinetic Theory of Ideal Gases1h 50m
22. The First Law of Thermodynamics1h 26m
23. The Second Law of Thermodynamics3h 11m
24. Electric Force & Field; Gauss' Law3h 42m
25. Electric Potential1h 51m
26. Capacitors & Dielectrics2h 2m
27. Resistors & DC Circuits3h 8m
28. Magnetic Fields and Forces2h 23m
29. Sources of Magnetic Field2h 30m
30. Induction and Inductance3h 38m
31. Alternating Current2h 37m
32. Electromagnetic Waves2h 14m
33. Geometric Optics2h 57m
34. Wave Optics1h 15m
35. Special Relativity2h 10m

33. Geometric Optics

Reflection of Light

Physics

33. Geometric Optics

Reflection of Light

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7:38 minutes

Problem 5

Textbook Question

The mirror in FIGURE EX34.5 deflects a horizontal laser beam by 60°. What is the angle ϕ?

Verified step by step guidance

Identify the relationship between the angles of incidence and reflection. According to the law of reflection, the angle of incidence is equal to the angle of reflection.

Recognize that the total deflection angle of the laser beam is given as 60°. This deflection angle is the sum of the angle of incidence and the angle of reflection.

Let the angle of incidence be denoted as θ. Since the angle of incidence equals the angle of reflection, the total deflection angle can be expressed as 2θ = 60°.

Solve for θ by dividing both sides of the equation by 2: θ = 60° / 2.

The angle ϕ is the angle between the mirror's surface and the incident beam. Since the angle of incidence θ is measured relative to the normal to the mirror, ϕ can be calculated as ϕ = 90° - θ.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Reflection of Light

Reflection of light occurs when a light beam strikes a surface and bounces off. The angle of incidence, which is the angle between the incoming beam and the normal (a perpendicular line to the surface), is equal to the angle of reflection. This principle is crucial for understanding how mirrors work and how they redirect light beams.

Angle of Deflection

The angle of deflection refers to the angle by which a beam of light is redirected after striking a surface, such as a mirror. In this context, if a laser beam is deflected by a certain angle, it is essential to understand how this angle relates to the angles of incidence and reflection to determine the resulting angles in the system.

Geometry of Angles

Understanding the geometry of angles is vital for solving problems involving reflections. In this scenario, the total angle change can be calculated by considering the initial angle of the beam, the angle of incidence, and the angle of reflection. This geometric approach allows for the determination of unknown angles, such as ϕ, based on the known deflection.

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