Unit 2: OPTICS

What is Light?

What do you already know?

• Answer the questions on pg 461

What is Light?• A ‘piece’ of light energy is called a photon• Photon: a bundle (quantum) of electromagnetic

(light) energy.-is always in motion-has a constant speed in a vacuum

(speed of light)c = 2.998 x 108 m/s. (1.07925285 × 109km/hr)

• Light travels very fast– It could circle Earth’s equator about 7.5 times per

second!!• Light travels in waves and these waves travel

in straight lines• Creates sharp shadows

• A medium is any substance that energy can be transferred through

• Light does NOT require a medium- it is transferred through radiation (can travel through a vacuum)

• Light is a combination of electricity and magnetism (electromagnetic)

Wavelength

Easiest to measure crest to crest or trough to trough

Wavelength

Electomagnetic Spectrum

• The range of electromagnetic waves (from low to high energy)

Visible Light Spectrum

• White light is made up of:Red, orange, yellow, green, blue, indigo and

violet(ROY G BIV)

Show Demo

• Visible Light:– Electromagnetic waves that the human eye can

see– Ex. red light

• Invisible Light:– Electromagnetic waves that the human eye cannot

see– Can still detect them and use them for many

things– Ex. radio waves

Electromagnetic Waves in our Society

• Use the chart on pg 466 to complete your worksheet

Visible Light experiment

• Complete the ‘Try This’ activity on pg 467

How does this work?• A triangular prism slows down the speed of light• Each colour is slowed differently because of

differing energy levels- this separates white light into different colours!

Homework

• Read pages 463 - 467• Pg. 469 # 3(read p 464), 4, 5, 8, 9, 11