Understanding the Spectrum, Reflection, & Refraction

Ms. Majewski

-If a light wave has a wavelength of 400 x 104 m, what is its frequency?

-If a light wave has a frequency of 2 x 109 Hz, what is its wavelength?

Check your AnswersUse the speed of light: 3.0 x 108 m/s. Show all work and include units.

75 Hz

0.15 m

How Light Rays work… When a ray of light strikes a plane

mirror, the light ray reflects off the mirror.

http://www.physicsclassroom.com/mmedia/optics/lr.cfm

*Shows what this looks like in an animated image.

The Law of Reflection

According to the law of reflection…

the angle of incidence = the angle of reflection

The angle of incidence: the angle between this normal line and the

incident ray. The angle of reflection: the angle

between this normal line and the reflected ray.

Law of Reflection Image: Fill it in

Mirror

Source

Normal

- Angle of Reflection

- Angle of Incidence

Long wavelengthLow frequencyLow energy

Short wavelengthHigh frequencyHigh energy

1. What is the order of colors starting at RED and increasing in frequency? Use full names and keep them in order.

2. If you were to start at RED of Visible Light, and decrease frequency into the other parts of the electromagnetic spectrum, what three types of electromagnetic waves would you encounter? Give them in order of decreasing frequency.

3. If you were to start at Violet, and increase frequency into the other parts of the electromagnetic spectrum, what three types of electromagnetic waves would you encounter? Give them in order of increasing frequency.

Check your Answers

• Red, Orange, Yellow, Green, Blue, Indigo, Violet

• Infrared, Microwaves, Radio Waves

• Ultraviolet Light, X-Rays, Gamma Rays

Review: Refraction Caused by the change in speed experienced

by a wave when it changes medium.

The Amazing Archer Fish http://

www.physicsclassroom.com/Class/refrn/u14l1f.cfm

Index of refraction (n)

Basically it says how hard it is for light to travel through a media.

The higher the number the harder it is to travel.

Snell’s Law

Practice A person is shinning a flashlight (through air

1.0) into an unknown medium (n2). The light enters at 28° to the normal line. It becomes 10 °within the 2nd medium. Calculate the index of refraction of the 2nd medium?

28°

Snell’s Law - Example

INDEX OF REFRACTION

INDEX OF REFRACTION EQUATION

Index of refraction(n)= speed of light in a vacuum(c)

speed of light in material (v)

Practice Problem:Calculate the speed of light in water. Water has an index refraction of 1.33.

1.33 = 3x108m/s v

v = 225563909.774 m/s