If the dna in every cell for one individual the same, how is it possible to have different cell types with different phenotypes of physical features?

Genes are turned "on" and "off" to code for specific proteins.

Explanation:

The DNA is the genetic make up of the cell and contains the genetic material that code for genes, proteins and the whole functioning of the organism. The DNA in every cell is usually the same, but the reason why we have different cell, organs and systems functioning differently is because of the genes which are turned off or on. For instance in the eye, the gene for the retina will be turned on while that in the muscle will be silenced or turned off. Tge genes needed are turned on to code for proteins that carry out the desired function thus creating diversity and specialization in functions.

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.