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.
12. A Krypton B laser will require less than 1,000 ergs/cm2 to record a hologram on which emulsion(s) ?
Your Answer is
Correct Answer is H
Explanation
Look at the figure first, the wavelength corresponding to Krypton B is 674 nm, so when the abscissa is 674, the ordinates of Emulsion 2 & 3 are both less than 1000