Section 3 review
Ray diagrams are used to trace the path of light rays through an optical system. The angle of incidence and angle of reflection are measured with respect to the normal to the reflecting surface. The law of reflection states that the angle of incidence equals the angle of reflection. When light is reflected from a flat mirror, an image forms behind the mirror at the point from which the reflected rays appear to diverge. The image distance for a flat mirror equals the object distance, which is the distance between the object and the reflecting surface. Read the text aloud
incident ray, reflected ray, normal, law of reflection, angle of incidence, angle of reflection, image

θ i = θ r

Review problems and questions

  1. Does the law of reflection apply to specular reflection, diffuse reflection, or both types of reflection?
  2. Read the text aloud Show
Mirror reflection in the painting <i>Venus and Cupid</i> by Diego Velasquez
  1. In the Diego Velasquez work Venus and Cupid, the artist depicted the subject looking into a mirror. Is she looking at herself in the mirror? Why or why not? Read the text aloud Show
  1. Some interior designers place a large, flat mirror on one wall of a room to make the room feel bigger. Explain their argument using the physics of mirrors and image formation. Read the text aloud Show
  1. A laser beam hits a mirror at an angle of incidence of 65°.
    1. What is the angle of reflection of the laser beam?
    The laser then hits a mirror perpendicular to the first.
    1. What is the angle of incidence of the laser to this mirror?
    2. What is the angle of reflection from the second mirror? Read the text aloud Show
  1. A young man is standing 87.3 cm in front of a flat mirror. He sees the image of a light bulb at an angle of reflection of 57.9°. The light bulb is physically located 175 cm in front of the mirror. What is the image distance for the image of the bulb in the mirror (i.e., the distance behind the mirror at which the image of the bulb appears)? Read the text aloud Show
  1. In drawing a ray diagram, a student drew an incident ray that passed along a normal to the surface of the mirror. What is the value of the angle of reflection? Read the text aloud Show

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