What did Jagendorf's experiments confirm? A. A sodium ion gradient across the thylakoid membrane led to the production of ATP.
B. A proton gradient across the thylakoid membrane led to the production of ATP.
C. A proton gradient within the stroma led to the production of ATP.
D. A sodium ion gradient within the stroma led to the production of ATP.

the question isn't complete here so i can't right an answer '_'

measuring light intensity

light meters can be used to measure light intensity. the meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

errors can be made when measuring light intensity by accidentally shading the light meter. the reliability of the results can be checked by taking many samples.