# Can the human eye see the images of 300 nm light on a screen through a diffraction grating?

In my textbook there is a question as follows:

A diffraction grating with 200 lines per mm is placed between a monochromatic light source and a screen. The distance from the grating to the screen is 2.5 m and the distance between the two 2nd order images is 60 cm on the screen. Calculate the wavelength of the monochromatic light.

$$d=5x10^{-6}m$$

$$y=0.3m$$ $$x=2.5m$$ $$n=2$$ $$sin\theta =\frac{y}{\sqrt{x^2+y^2}}$$ $$\lambda=\frac{d sin\theta}{n}=297 nm$$

But the human eye cannot see 300 nm and shorter wavelengths.

Is there something happening due to the presence of the grating and the screen that allows viewing of these images or would these images not be viewable to the human eye as I suspect ?

My understanding is that the images are not viewable by the human eye.

I also understand that the point behind the question is just to practice using the formula and to not worry too much about the numbers. But I like to think about the real situation when I work through problems.

• But the example doesn't suggest that the pattern is viewed directly by human eyes. It can be recorded by a photographic film, an electronic light sensor etc. Commented Mar 17, 2023 at 16:19
• @Ruslan That's true Ruslan. But do you agree that for 300 nm viewing with the human eye is impossible ? Commented Mar 17, 2023 at 17:13
• There is nothing special about a diffraction grating that would allow the human eye to see 300nm light. A human would not be able to see the diffraction pattern. Commented Mar 17, 2023 at 17:20
• @Kantura with intact human eyes it's impossible. Aphakic eyes might be able to see it. Commented Mar 17, 2023 at 17:59