Light – a wave, a ray, or a particle?

Law of Reflection – ray optics view

But light’s not really a ray Why can we get away with acting like it is? Do ocean waves act like rays of light? Why can we get away with acting like it is? Do ocean waves act like rays of light? What’s the real reason light reflects symmetrically around the normal? What’s the real reason light reflects symmetrically around the normal?

Discussion question: How tall must a flat mirror hanging on the wall be in order for a person to see their feet and their eyes without moving with respect to the mirror? 1. As tall as the person 2. Half the height of the person 3. ¼ the height of the person

Hard Work Today, many have forgotten the value of work. Some falsely believe that the highest goal in life is to achieve a condition in which one no longer needs to work. President David O. McKay ( ) was fond of saying, "Let us realize that the privilege to work is a gift, that power to work is a blessing, that love of work is success." Work is not a matter of economic need alone; it is a spiritual necessity. -- BISHOP H. DAVID BURTON -- BISHOP H. DAVID BURTON

Reading question: The speed of light in glass is _________ the speed of light in air. 1. Less than 2. The same as 3. Greater than

Snell’s law describes refraction: the bending of light when it enters a medium.

The rolling barrel - a sort of ok- ish analogy that is often used

The wave physics behind Snell’s law What changes when the light enters glass? What changes when the light enters glass? What stays the same? What stays the same?

There’s actually more than one speed... Dispersion, phase velocity, group velocity

Light enters a piece of plate glass which is 3 mm thick and has an index of refraction of 1.5. It enters the glass at an angle θ 1 relative to the normal. It exits the glass at an angle θ 3 relative to the normal. Which of the following is true? 1. θ 3 is greater than θ θ 3 is less than θ θ 3 is equal to θ It depends on information I haven’t given you

Snell’s Law

Consider refraction through three materials. Now remove the middle material. Consider refraction through three materials. Now remove the middle material. A. Angle  3 is smaller than before B. Angle  3 is the same in both C. Angle  3 is greater than before

Light is travelling in glass with an index of refraction of 1.5. It strikes the surface of the glass at an angle of 85 degrees from the normal. Some of the light transmits, some reflects. What direction will the two beams travel?

n 1 = n 2 = θ1θ1 θ2θ2 θ1θ1 θ2θ2

93% Transmission over a km!

Discussion question: A fish swims below the surface of the water. The observer sees the fish at A. A greater depth than it really is B. The same depth C. A smaller depth than it really is.

Looking at things in a mirror

Virtual image The light does not actually come from that point—it only looks like it does. You have to look into the mirror to see it. The light does not actually come from that point—it only looks like it does. You have to look into the mirror to see it.