Since the light bulb from the previous experiment is hot and emits visible light, we want to know if light and heat are the same thing, or if they different?
Q1: Are light and heat the same thing?
Q2: Can you have one without the other?
Q3 What is light?
Q4 What is heat?
Q5 How does heat and light affect matter?
Students did a free write to the questions 1 & 2, then we discussed it as a class.
Next, after much discussion, the students then defined what heat and light were - and we then discussed that; which then opened us up to the experiments.
Q2: Can you have one without the other?
Q3 What is light?
Q4 What is heat?
Q5 How does heat and light affect matter?
Students did a free write to the questions 1 & 2, then we discussed it as a class.
Next, after much discussion, the students then defined what heat and light were - and we then discussed that; which then opened us up to the experiments.
Experiment 1
Space Heater + radiometer
- Experiment:
- We wanted to know if the space heater, which generates a lot of heat and a red glow has radiant energy.
- Results:
- On: We placed the radiometer in front of the space heater, and it spun.
- Reflection:
- This means that the space heater is generating radiant energy. This means so far that heat and light are the same thing thus far. This also proves that heat traveling from the space heater travels in waves - the reason why we are saying this is because the heat from the space heater is reflecting off of the silver dish.
Experiment 2
Hot Plate + radiometer
- Experimental Design:
- The hot plate generates a lot of heat, but no glowing red/orange light. We wanted to know if the radiometer will still spin under these conditions.
- Results:
- By turning the burning plate on its side & placing the radiometer in front of it - the radiometer still spun.
- Reflection:
- This means that heat can still generate radiant energy.
- Question: Does this mean that heat is radiant energy and not light?
Experiment 3
LED Light bulb and Radiometer
- Experimental Design:
- An LED light bulb does not generate a lot of heat, if at all. It is very cool to the touch. We want to know if it will make the radiometer spin as well.
- Results:
- The LED light bulb does make it spin, albeit not very fast.
- Reflection:
- This means that light is a form of radiant energy, but it doesn't seem to have as much energy as the sources that were hot. It would seem that heat is more of a radiant form of energy than light is at this point. Nevertheless, there is a weak dissociation that light and heat are two separate forms of energy.
experiment 4
LED on a Solar Panel & Electric Light Indicator
- Experimental Design:
- Since solar panels generate electricity, we want to know if an LED light bulb will generate electricity.
- Results:
- The LED light bulb does turn on the indicator very well.
- Reflection:
- This shows that the light from the LED bulb does indeed make electricity.
experiment 5
Hot blow dryer on a solar panel & electrical indicator
- Experimental Design:
- Since we know that the LED light bulb does barely make the radiometer spin, and turn on the electrical indicator from the solar panel, we want to know if the heat from the hair dryer, (which makes the radiometer spin very quickly), will turn on the light indicator.
- Results:
- The hair dryer did NOT turn on the electrical light indicator from the solar panel. This means that heat, which may have radiometric properties is not the same thing as light energy.
Other tests performed but not listed:
- space heater on / off
- Rub hands together + radiometer
- Hair Dryer & radiometer (cool v hot)
- Laser & radiometer (wht v black)
Summary
- Light is related to heat, but they are NOT the same form of energy.
Had we had more time, we would also find the following:
- Heat will always generate light, but there are many ways to generate light. Heat is only 1 way.
- The reason why the hot plate / solar space heater made the radiometer spin is due to different bands of light that we cannot see. (*See infra-red)
- The reason why the radiometer spins is because light energy turns into heat energy.
- How it works:
- If the light flashes on the white side, the light is reflected.
- If the light flashes on the black side, the light is absorbed and turned into heat.
- Once the black pane turns the light energy into heat energy, the atoms of air absorb the heat energy (via conduction) and push off.
- Since pushing is a force, newtons 3rd law states that for every action, there is an equal and opposite reaction. Therefore, the pane goes in the direction indicated below.
- If the light flashes on the white side, the light is reflected.
- How it works: