Lesson 6 — 6.4 + 6.5

• Speed of light + reflection
• Middelbare school
• havo, vwo
• Leerjaar 2

Science P4

The speed of light

&

Reflection

This lesson

• Completing the speed of light
• Reflection — Phet simulation
• The practical

Learning 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

• 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.

Recap

Speed of light

What did we learn about the speed of light?

what is the speed of light?

300 000 000 m/s

Of  300 000 km/s

What is the symbol for the speed of light?

c

'Celerity'

Latin for Swift

In astronomy light is used as a unit of...

Distance

Light years

Measuring the speed of light

Calculations with the speed of light

Calculate how long it would take in minutes for light to travel from the Sun to the Earth in.

Given

• Speed of light = c = 300 000 000 m/s = 300 000 km/s
  
• Distance = 150 000 000 km
  

Asked

• How long does it take for light of the sun to reach the Earth.
  

Formula

• v = d/t        t = d/v
  

Calculation

• t = 150 000 000 / 300 000 = 500s
  
• 500s / 60 = 8.3 minutes (8 minutes and 18 seconds)
  

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 9 460 000 000 000 kilometers per year.

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

Given

• Speed of light in km/year = 9 460 000 000 000
• distance proxima centauri Earth = 40 208 000 000 000

Asked

• How many light years away is Proxima Centauri?
  

Formula

• -
  

Calculation

40 208 000 000 000/ 9 460 000 000 000 = 4.2 light years

• 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 reaches 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
  

6.4 Reflection

• Plane mirror
  
• Image
  
• Virtual image — Real image
  
• Types of reflection
• The law of reflection
  
•  Incident ray — reflected ray
• Angle of reflection

Phet simulation

• Search for: Phet bending Light 
• Experiment with this independently for 5 minutes
• What can you learn about reflection? Find out as much as you can 
• Write down what you learned

Link

law of reflection

Homework

Read: 3.4 + 3.5

Do: Workbook exercises 6.4 (Including E)

The electromagnetism practical

Learning 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