B4 The Rate of Photosynthesis cont.... (page 53) Flashcards
What is ‘The Inverse Square Law’?
It tells us that the intensity of light is inversely proportional to the square of the distance from the source. Therefore when the light is moved twice as far from the plant it will receive a quarter of the energy.
(the inverse square law links Light Intensity and Distance).
With the Pondweed experiment, when the lamp was moved away from the pondweed, what happens regarding the light that reaches the pondweed?
The light that reaches the pondweed decreased (you could say this as :- As the distance increases, the Light intensity decreases. In other wards, distance and light intensity are Inversely Proportional to each other)
Explain how Inverse Square Law is Written?
1
Light intnensity (a) ______________
distance (d)²
(the (a) symbol means proportional to symbol)
(1 means putting one over the distance)
(² means the distance is squared)
please look at diagram on page 53
The light intensity decreases in proportion to the square of the distance - this is called interse square law.
What do the Inverse Square Law mean?
It means f you halve the distance, the light intensity will be four times greater, and if you third the distance, the light intensity will be nine times greater. Likewise, if you double the distance, the light intensity will be four times smaller and if you treble the distance the light intensity will be nine times smaller
You can use 1/d² as ameasure of light intensity.
Use the Inverse square Law to calculate the light Intensity when the lamp is 10cm from the pond weed?
1) Use the formula 1
___
d²
2) fill in the values - you are given, the distance
3) calculate the answer
Light Intensity = 1
___
d²
Light intensity = 1
___
10²
= 0.01 a.u. (a.u. - stands for arbitrary Units
How can you officially create the ideal enviornment for plants to grow and why?
Grow them in a green house. Greenhouses help to trap the suns heat and makesure that the temperatures doesn’t become limiting. In the winter, a farmer or gardener might use a heater as well, to keep the temperature at the ideal level. In sumer it could get too hot, so they might use shades and venitlation to cool things down.
What is always needed for photosynthesis?
Light, so commerical farmers often supply artificial light after the sun goes down to give their plants more quality photosynthesis time.
How can farmers and Gardeners increase the level of carbondioxide in the greenhouse?
By using a paraffin heater to heat the greenhouse. As paraffin burns it makes carbon dioxide as a by-product.
Keeping plants enclosed in a greenhouse makes it easier to keep them free from what?
Pests and diseases, and farmers can add fertilisers to the soil as well to provide all the minerals needed for healty growth.
Why is it important for the farmer to keep the conditions just right for photosynthesis in a greenhouse?
Sorting all this costs money, the plants will grow much faster, and a decent crop can be harvested more often, which can then be sold.
Why is it important for the farmer to supply just the right amount of heat, light etc?
so the plants grow well, but not more than the plants need, as this would be wasting money.
An experiment was carried out to find out the effect of temperature on the rate of Photosynthesis. Name two variables that should have been controlled in the experment? (2 marks)
Light Intensity (1 mark)
CO2 (1 mark)
A plant is moved from 15cm away from its light source to 5cm away from it’s light source. Using the Inverse Square Law show that the light Intensity becomes nine times greater? (3 marks)
1
Light intensity = ________________
distance²
1 ÷ 15² = 0.00444…a.u. (1 mark)
1 ÷ 15² = 0.04a.u. (1 mark)
0.04 ÷ 0.00444…= 9 (1 mark)
