Light Intensity and Distance from a Light Source Flashcards

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What is meant by light intensity in photosynthesis experiments?

Light intensity is how much light energy reaches the plant each second.

How does increasing light intensity affect the rate of photosynthesis, if no other factor is limiting?

If no other factor is limiting, a higher light intensity makes the rate of photosynthesis increase.

In a lab experiment, how can you increase the light intensity reaching a pondweed?

You can move the lamp closer to the pondweed to increase the light intensity.

What is the relationship between light intensity and distance from a light source?

Light intensity is inversely proportional to the square of the distance from the light source (intensity ∝ 1 ÷ distance²).

If you double the distance between a lamp and a plant, what happens to the light intensity on the plant?

The light intensity becomes one quarter of what it was before.

In a photosynthesis experiment with a lamp and pondweed, what is usually the independent variable?

The independent variable is the distance between the lamp and the pondweed.

In a photosynthesis experiment with a lamp and pondweed, what is usually the dependent variable?

The dependent variable is the rate of photosynthesis, often measured by counting bubbles per minute.

Why is it important to keep temperature and carbon dioxide level constant when testing light intensity and distance?

They must be kept constant so that only light intensity changes, making the test fair and the results valid.

Why is an LED lamp often used in photosynthesis experiments on light intensity?

An LED lamp is used because it gives light but produces less heat, so the temperature stays more constant.

Why might scientists plot rate of photosynthesis against 1 ÷ distance² instead of against distance?

They use 1 ÷ distance² because it is directly proportional to light intensity, so the graph is a straight line.