# The Electromagnetic Spectrum 5

Year 09 Topic 1: The Electromagnetic Spectrum.
9 Learning Opportunities From Monday the 30th of March until Friday the 1st of May
Learning Opportunity 5: The Spectrum and the Atmosphere
This Learning Opportunity has Four tasks to do.
Target Time: 60 minutes.
Aim: Describe the differences in the behaviour of waves in different parts of the EMS

Task 1: Write four definitions. Use a video to help.

Write a definition of Absorbed, Transmitted, Reflected and Refracted in terms of waves.
When waves move between the boundaries of different materials, there are 4 different things that can happen to the wave.
Copy these words and say what they mean (write a definition). Use the video here to help with the first 3 and previous lessons to look at refraction.
Absorbed
Transmitted
Reflected
Refracted
Check your answers at the end of the blog.

Task 2:  Write a paragraph about how the spectrum is absorbed.

Read this paragraph, then answer the questions.
How does the Earth’s atmosphere absorb the different parts of the Electromagnetic Spectrum (EMS)?
Energy emitted from stars can be at any wavelength of the EMS. Our atmosphere will absorb some wavelengths and refract, reflect or transmit other wavelengths. The figure below shows how different wavelengths are absorbed by the atmosphere.

Describe how wavelength affects absorption.
Check your answers at the end of the blog.

1) What % of gamma rays are absorbed?
2) What % of X-Rays are absorbed?
3) What is the lowest % of UV that is absorbed?
4) Roughly what % of light is absorbed?
5) What is the highest % of IR that is absorbed?
6) What is the range of % of absorption for microwaves?
7) What % of short-wave radio waves are absorbed?
8) What % of long-wave radio waves are absorbed?

Task 3: Check you answers and try an assessment question.

Task 1: Absorbed – taken in, or soaked up. A sponge absorbs water. Transmitted – goes through. A window transmits the light straight through. Reflected – when light bounces off a surface. The light reflects off the mirror. Refracted – when light bends, going from one material to another, due to a change in speed.
Task 2: 1) 100%. 2) 100%. 3) about 10%. 4) about 25%. 5) 80%. 6) From 100 to 0 so 100%. 7) 0%. 8) 100%.

Now please complete the following exam questions. When you have finished, mark and correct your answers. Add a final comment to your work saying what you found easy and what you found more challenging
The Earth’s atmosphere absorbs electromagnetic radiation.
The diagram shows how the amount absorbed changes with wavelength.

(i)   How much of the visible light from space is absorbed as it passes through our atmosphere?
Write down your answer. (1)
A  0%
B  10%
C  90%
D  100%

(ii)  Large telescopes which collect visible light to explore the Universe are usually placed near the tops of mountains.
Suggest why radio telescopes do not have to be placed high up a mountain. (1)

(iii) One theory of the origin of the Universe predicted that there should be cosmic background radiation with a wavelength of about 1 mm.
Explain why scientists had to wait until the development of space flight before they could study this radiation in detail. (2)

Task 4: Final answers and challenge.

Check your answers

Challenge
Find the four most important facts from this article:
https://science.nasa.gov/ems/01_intro