Lesson 5 — 6.3

• The speed of light
• Middelbare school
• havo, vwo
• Leerjaar 2

Science P4

The speed of light

This lesson

• Quiz about the speed of light
  
• What we have to learn about the speed of light this lesson
  
• Bonus: How was the speed of light first measured?

Goals

• The symbol of speed of light in physics
  
• Explain how the speed of light us used as a unit of distance
•  Explain how astronomers use light to study space
•  Be able to do calculations using the speed of light

• During class – have a question, raise your hand.

• When working  together, do not talk with or shout to people on the other side of the class.

• While working independently, do not disturb the class.

•  Participate seriously in the class (also when working with our phones). do not make noise, inappropriate jokes, chat with everyone around you, shout through the class, etc.

• After one warning, when you break the rules again— You go to olc 2 with extra work.

Agreements from previous lesson

• The classes in the coming two weeks will be more interactive (Kahoot, quizzes, things like that).
  

• There will be more demonstrations in the sciences classes.
  

•  Working in pairs or groups more.
  

• We will keep up the current rules
  

• If this works well for the coming two weeks, we will continue this.
  

The speed of light

What is the speed of light?

1. 5 000 km/s
2. Instant
3. Unknown
4. 300 000 000 m/s

The speed of light is the absolute maximum

1. Correct
2. You can never know, maybe something can go faster
3. There is no way to know
4. Incorrect

Since the speed of light is so unique in Physics, it has been given a name. What is this name?

1. S/L
2. c
3. Max. Speed
4. Absolute speed

Why 'c'?

Comes from 'Celerity'

Latin for swift

The light of the sun reaches the earth instantly.

1. True
2. False

If a person runs towards a light ray, they will measure the speed of light to be?

1. Exactly the speed of light
2. The speed of light + his running speed
3. slower than the speed of light

If a rocket traveling at 50% the speed of light towards a light ray, they will measure the speed of light to be?

1. Exactly the speed of light
2. The speed of light + it's traveling speed
3. slower than the speed of light

If a rocket traveling at 50% the speed of light away from a light ray, they will measure the speed of light to be?

1. Exactly the speed of light
2. The speed of light - it's traveling speed
3. slower than the speed of light

Astronomy

A light year is a unit of...?

1. time
2. speed
3. distance

Light is the only thing that can be measured for astronomers to use to study the universe

1. There must be more the can measure to study the universe.
2. Light is the main thing , but there are several other ones.
3. Light is the only thing that can be measured to study the universe.
4. Light is the main , but there is one other thing.

If you look up to the stars, the things you see are

1. Exactly the way they are in space
2. You are looking into the past

6.3 The speed of light

The speed of light

• 300 000 000 m/s
  
• this is called 'c'
  

Light — as a distance unit

• Light seconds
  
• light minutes
  
• light hours
  
• light years (ly)
  

Exercise

The closest star to our sun is Proxima Centauri. This star is 40,208,000,000,000 km away from our sun. 

The speed of light is 300 000 000 m/s

How many light years away is Proxima Centauri from our sun?

• The speed of light = 300 000 000 m/s — called 'c' in physics.
  

• Light is used as a measure of distance (light years).
  

• Astronomy studies the universe through the information in the light that reachers earth.
  

• to measure the speed of light, technology had to invented that measures time in small enough intervals to be able to detect it.
  

• calculations using the speed of light
  

Study §6.4

Reflection

Search for: 

Phet bending Light 

Link

Goals

• Name the speed of light and it's name in physics
  
• Explain how the speed of light us used as a unit of distance
•  Explain how astronomers use light to study space
•  Be able to do calculations using the speed of light