Download Name: Period: ______ Date: Light/Astronomy Study Guide What are

Name: ___________________________________ Period: ___________ Date: _____________________
Light/Astronomy Study Guide
1. What are the energy transformations in a flashlight?
Chemical  electrical  Light + Heat
2. Draw a diagram of what it would look like to shine a flashlight on the wall (Without rays).
3. Draw a ray diagram of a flashlight shining on a person who is standing a meter in front of the
wall.
4. Describe the behavior of light.
Light will behave at times like a wave, and at times, like a particle. When light creates a shadow,
it acts more like a particle. When light creates interference patterns in the double slit
experiment, or when we talk about its wavelength, it acts more like a wave.
5. If have a light source shining onto a wall, and you start at the wall, and move towards the light,
what will happen to your shadow? Why?
The shadow will get bigger, because you are blocking more of the light rays. Light spreads out as
it moves away from its source.
6. What is the speed of light?
300,000,000 m/s
For questions7-9, look back at the homework you did on pages 149-157 for help:
7. How do you calculate the speed of a wave?
𝑠𝑝𝑒𝑒𝑑 = 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 × 𝑤𝑎𝑣𝑒𝑙𝑒𝑔𝑡ℎ
𝑣 =𝑓×𝜆
Name: ___________________________________ Period: ___________ Date: _____________________
8. If you have a slinky that is 3m long, and decide to make waves with a wavelength of 2m and it
takes 40 seconds for there to be ten vibrations, what is the speed of the wave?
𝑣 =𝑓×𝜆
𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑤𝑎𝑣𝑒𝑠
𝑓=
𝑡𝑖𝑚𝑒
10 𝑤𝑎𝑣𝑒𝑠
𝑓=
40 𝑠
𝑓 = 0.25 𝐻𝑧 (𝑠 −1 )
𝑣 = 0.25 𝐻𝑧 × 2 𝑚
𝑣 = 0.5 𝑚/𝑠
9. What frequency of purple light (400nm)?
𝑣 =𝑓×𝜆
𝑣
𝑓=
𝜆
𝜆 = 400 𝑛𝑚 = 4 × 10−7 𝑚
3 × 108 𝑚/𝑠
𝑓=
4 × 10−7 𝑚
𝑓 = 7.5 × 1014
10. What is the difference between amplitude, frequency, and wavelength?
Amplitude is the high of the wave above the mid line, the frequency is the number of waves per
second, and the wavelength is the distance between two consecutive crests or troughs.
11. Which has more energy, red light or blue light? Which has the higher wavelength?
Red light has less energy and a longer wavelength, and blue light has more energy and a shorter
wavelength.
Astronomy
12. What factors go into how bight a star appears to us here on earth?
Its size and temperature, and along with that is its luminosity
13. If star A appears blue, and star B appears red, wat can we infer about the differences between
them?
Star A is a hotter star than then star B
14. How is a Hertzprung-Russel diagram useful? What does it look like?
It allows us to classify the stars. For a great picture, look at page 727 in your blackbooks.
15. Describe a life cycle of a very massive star.
Nebula  protostar  Main Sequence Blue Supergiant  Red Supergiant  Super Nova 
Black Hole
Name: ___________________________________ Period: ___________ Date: _____________________
16. Describe the life cycle of low mass star.
Nebula  protostar  Main Sequence Star Red Giant  White Dwarf
17. What process fuels a star, and what are the process that cause it to die?
The fusion of hydrogen in to helium fuels a star (balance between explosion outwards, and
gravity inwards) and when this fuel runs out, the star begins to die.
18. Where/when are the following elements created:
a. Light elements light hydrogen, helium, and lithium
Formed in the big bang
b. Heavier elements light oxygen, and iron
Formed in starts
c. Elements heavier than iron
Formed during a supernova
19. Explain “red shift”, and how it is useful.
This is the result of the Doppler effect on the light from galaxies that are moving away from us.
The waves that are going towards us are expanded to so that the normal spectrum of elements
are shifted in the red direction.
20. Describe the three main pieces of evidence that we have for the big bang theory.
1. With redshift, we can tell that all other galaxies are moving away from us.
2. Hubble and his colleagues detected background x-ray radiation from the big bang.
3. Einstein’s equation 𝐸 = 𝑚𝑐 2 means that it was possible for there to be only energy before
the big bang, and we could still get all the matter we have today.