Passage II
A hologram is a three-dimensional image produced when light from a laser shines on a film coated with a material called a holographic emulsion. The laser provides the light at a specific wavelength.
The figure below shows the light energy per unit area (in ergs/cm2) required to create a hologram on 3 different emulsions using gas lasers. For example, an Ar laser must produce 100 ergs/cm2 to create a hologram on Emulsion 2. The figure also shows how the sensitivity to light of each emulsion and the light energy per unit area required to create a hologram on each emulsion vary with the wavelength of light used.
9. Based on the figure, which of the following lasers produces a beam of light closest in color to red?
Your Answer is
Correct Answer is D
Explanation
Look at the picture, red is written under the abscissa 650, so the wavelength of red light is about 650nm, and the Krypton B (647 nm) shown in the picture is closest to 650