Measuring the rate of photosynthesis

• What is the purpose of measuring the rate of photosynthesis in the experiment described?


  To see how changing light intensity affects the rate of photosynthesis
• How is oxygen production used in the experiment to indicate the rate of photosynthesis?


  The oxygen released collects in a capillary tube, and its length is proportional to the volume of O₂ produced
• What should be controlled in the experiment to ensure accurate results?

  Variables such as temperature and time the pondweed is allowed to photosynthesize
• How many times should the experiment be repeated with the light source at the same distance?

  Twice
• What is the purpose of repeating the experiment with the light source at different distances?

  To observe how light intensity affects the rate of photosynthesis
• How can the apparatus be altered to measure the effect of temperature on photosynthesis?


  By placing the test tube of pondweed into a water bath at a set temperature
• How can the effect of CO₂ on photosynthesis be measured in the experiment?


  By dissolving a measured amount of sodium hydrogencarbonate in the water
• What does the inverse square law describe in relation to light intensity and distance?


  • As distance increases, light intensity decreases
  • Light intensity decreases in proportion to the square of the distance
  • Written as: light intensity ∝ 1/d²
• What happens to light intensity when the distance from the pondweed is doubled?


  Light intensity decreases to one-fourth of its original value
• How does the inverse square law apply when the distance is halved?


  Light intensity becomes four times greater
• What is the relationship between distance and light intensity according to the inverse square law?


  Distance and light intensity are inversely proportional
• Calculate the light intensity when the lamp is 10 cm from the pondweed using the inverse square law.


  Light intensity = $1/10^2 =$$0.01$ a.u.
• What does "a.u." stand for in the context of light intensity?


  Arbitrary units
• What does the concept of inverse proportion imply in the context of light intensity and distance?


  As distance decreases, light intensity increases
• What are the steps to calculate light intensity using the inverse square law?


  1. Use the formula: light intensity = 1/d²
  2. Substitute the known distance into the formula
  3. Calculate the answer
• What is the formula for the inverse square law?


  light intensity ∝ 1/d²
• What happens to light intensity if the distance is tripled?


  Light intensity becomes nine times smaller
• How does the inverse square law relate to the concept of light intensity in photosynthesis experiments?


  It explains how light intensity decreases with increasing distance from the light source