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 = x 10 8 m/s. ( × 10 9 km/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 Pg. 469 # 3(read p 464), 4, 5, 8, 9, 11