Science 8: Tues, Dec 18, 2012

Chapter 4 Test on Thursday! I hope everyone enjoyed the Holiday Review Stations! Here are the answers to the questions if you did not get them all:

Question 1:

Sketch the wave drawn below and label each part.

a) Amplitude

b) Crest

c) Trough

d) Wavelength   

Question 2:

What is the relationship between wavelength and frequency? What are the units for frequency and wavelength? Explain why with a drawing.

As wavelength increases, frequency decreases. Frequency is measured in Hertz (Hz) and wavelength can be measured in metres, centimeters, milimiters, etc.

Question 3:

What similarities do all the colours of light have? How are they different?

They all are waves; they make up white light. They are different because they have different frequencies and are different colours.

Question 4:

Describe the difference between wavelength and amplitude. Use a sketch in your explanation.

Wavelength is the width of a wave while aamplitude is the height of the wave from the rest position.

Question 5:

White light contains all the colours of a rainbow. How is it that a shirt appears blue when it is lit by a white light?   

A blue shirt absorbs all the colours from the white light except blue. The shirt will reflect blue light so our eyes see it as blue.

Question 6:

List five types of invisible waves from the electromagnetic spectrum. State if they are longer or shorter than visible light.

The three shorter waves are: gamma, x-rays and ultraviolet waves.
The three longer waves are: infrared waves, microwaves and radio waves.  

Question 7:

Say a series of waves passes under a dock:

a)What is the frequency of the waves if 14 crests pass in 7 seconds?

b) What is the frequency of the waves if 30 crests pass every 5 seconds?

c) What is the frequency when half a wave passes in 10 seconds?

a) 2 Hz

b) 6 Hz

c) 1/20 Hz 

Question 8:

Explain why the sky is blue! Explain what happens with a drawing.

White light from the sun enters the atmosphere but since blue light has a short wavelength, it hits the particles in the Earth's atmosphere and are scattered. We see the scattered blue light above us! The rest of the colours keep going into the Earth and we do not see them.

Question 9:

How can we get sunburned during a cloudy day but never when the sun is setting? From your understanding of how we get sunburned, what do you think sunscreen does?

This is because the UV rays which cause sunburns are scattered by the atmosphere, just like the short wavelength blue light so they never reach us. Sunscreen must protect our skin from UV light! (It absords the UV light so our skin does not).

Question 10:

Bill Nye video showed an example of internal reflection using a light and a tank full of water. What is internal reflection and what was the example he used?

Internal reflection is when light reflects off the inside surface of the medium. For example, Bill Nye showed internal reflection when the green light beam in the water tank reflected off the inside surface of the water! Another example was the fiber optics Bill Nye showed. The light reflects inside the fiber optic until it reaches the end.

Question 11:

What is refraction? Give an example you may see in everyday life.

What is reflection? Give an example you may see in everyday life.

Refraction is when light travels from one medium into another and changes angles because of this. It bends. A rainbow is the result of sunlight refracting in raindrops!

Reflection is when light bounces off a surface. For example, when light bounces off objects into our eyes, we can see the object. Also when light bounces off a mirror, it is reflected.

 

Question 12:

How did Sir Isaac Newton contribute to our understanding of white light? Describe the experiment he did.

Sir Isaac Newton discovered that white light is made up of all the different colours. His experiment was shining a beam of sunlight from a window into a prisim and seeing the visible spectrum of ligh (the rainbow) on the wall of his room.
 

Question 13:

Why are sunsets red? Explain with a drawing.

Sunsets are red because the short wavelength blue light (the same light we see when the sky is blue during the daytime) gets scattered away before we see it by the particles in the Earth's atmosphere. The rest of the light, mostly red and orange, travel to our eyes and we see the sunset as red and orange!

  

Question 14:

What is the difference between a compression wave and a transverse wave? Give examples of each type of wave.

Compression wave is when the particles are compressing as the wave travels. For example, compressing parts of a spring and letting it go, shows the wave travel along the spring. Sound waves are compression waves.

Transverse waves are waves that travel up and down. Some examples are water waves and light waves.