Why aren't vitamins a source of energy.

Vitamins are not a source of energy because they are essential nutrients that the body needs. Vitamins are needed to help the body function, they are not direct energy but they help it to break down fats, proteins, and carbs into sugars and enzymes that help it to improve.

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.