Do Now

What is the color of a light wave with a frequency of 5.65

x 1014 Hz?

Law of Reflection

Law of Reflection

Specular vs. Diffuse Reflection

The Law of Reflection is Always Observed (regardless of the orientation of the surface)

Specular vs. Diffuse Reflection

• Most objects which reflect light are not smooth at the microscopic level. Your clothing, the walls of most rooms, most flooring, skin, and even paper are all rough when viewed at the microscopic level. The picture at the right depicts a highly magnified, microscopic view of the surface of a sheet of paper.

Specular vs. Diffuse Reflection

specular reflection diffuse reflection

Diffuse Reflection

Specular reflection makes driving on rainy nights more difficult than on dry nights.

Specular reflection

Plane (flat) Mirrors

Image is • right side up• Left-right reverse • Same size as the

object • The same

distance from the mirror as the object

Image is upright.

• Ex. Ceiling doe not become the floor.

Left-right reversal

Plane (flat) Mirrors

• In order to view an object, you must sight along a line at that object; and when you do light will come from that object to your eye along the line of sight.

Virtual Image

• Light does not actually pass through the mirror, it only appears to be located inside the mirror

• Light appears to travel in straight lines, the human eye looks for the apparent origin of the light

Virtual image

Virtual Image

White Board it!

Challenge

• Consider the diagram at the right. Which one of the angles (A, B, C, or D) is the angle of incidence? ______ Which one of the angles is the angle of reflection? ______

• A ray of light is incident towards a plane mirror at an angle of 30-degrees with the mirror surface. What will be the angle of reflection?

• A ray of light is approaching a set of three mirrors as shown in the diagram. The light ray is approaching the first mirror at an angle of 45-degrees with the mirror surface. Trace the path of the light ray as it bounces off the mirror. Continue tracing the ray until it finally exits from the mirror system. How many times will the ray reflect before it finally exits?

Perhaps you have observed the image of the sun in the windows of distant buildings near the

time that the sun is rising or setting. However, the image of the sun is not seen in the windows

of distant building during midday. Use the diagram below to explain, drawing appropriate

light rays on the diagram.

• You might have noticed that emergency vehicles such as ambulances are often labeled on the front hood with reversed lettering (e.g., ECNALUBMA). Explain why this is so.

• If Suzie stands 3 feet in front of a plane mirror, how far from the person will her image be located?

EXIT QUIZ• 1. The

diagram below shows a light ray being reflected from a plane mirror. What is the angle of reflection?

2. An observer at point O sees the reflected light ray as shown in the diagram to the right. The image at point P that the observer sees is locatedat (1) A (2) B (3) C (4) D

3. Which phenomenon is illustrated by the diagram below?

(1) refraction (2) dispersion (3) regular reflection (4) diffuse reflection