Introduction to LightLight and the Electromagnetic Spectrum

The Importance of Light

• Light is the reason why we see everything around us.

• The light bounces off the object we are looking at, goes into our eyes, is focused on the back of our eye, a signal is created in the optic nerves and then our brain interprets the signal it receives from the optic nerves and makes a picture of what we are seeing.

• What is it about light that allows it to bounce off objects?

• What is it about light that allows our eye to focus it on our retina?

• In this slideshow, you’ll investigate the properties of light

What is Light Made of?

• Light is made up of waves

• It is also made up of tiny packets called photons.

• It is these two facts that make light a bit of weirdo in the scientific world; giving light a wave/particle duality.

• Einstein was one of the first to theorize about light and light behaviour.

• His theories were later proven through experiments and showed that even though light travelled in waves, it was affected by gravity, giving it mass.

• This meant light must also have a particle component to it

What is light made of? (cont’d)• A wave is a disturbance that transfers energy from one point to another.

•Properties of Waves–Waves can be described by the following properties:

1.Wavelength – the distance between waves, for example the distance between crests or troughs

2.Amplitude – the height from the centre of the wave to the top of the wave or from the centre of the wave to the bottom of the wave

3.Frequency – the rate of repetition of the waves

frequency

The Electromagnetic (EM) Spectrum

• Light is a form of energy

• The light we see (visible light) is only a small portion of waves that surround us everyday

• There is also light-like energy, that along with visible light, is called electromagnetic radiation.

•Electromagnetic radiation is a wave pattern made of electric and magnetic fields.

• The span of radiation from the longest wavelength in the radio wave region to shortest wavelength in the gamma ray region is called the electromagnetic spectrum. (see next slide for picture)

EM Spectrum (cont’d)

• Notice that next to the red side of the visible spectrum lies the infrared region and on the blue side of the visible spectrum lies the ultraviolet region.

QuestionsOn a separate piece of paper answer the following questions.

1. What is does light consist of?

2. Why is light unusual?

3. Name 3 properties used to describe light waves. Draw pictures to describe them.

4. What is electromagnetic radiation?

5. How is the electromagnetic spectrum organized?

Light Activity

• Go to page 390 in chapter 10 of your book and carry out the activity.

• Answer the questions from the activity in the title page.

• Note: if you do not have a digital camera at your site, then you can click on the video on the next slide to see what happens for part 1 of the activity.