A Level Physics Practice Exam

What is the effect of decreasing the wavelength of light in a diffraction grating experiment?

1. It decreases the angle of diffraction

2. It increases the angle of diffraction

3. It has no effect on the angle of diffraction

4. It reverses the direction of diffraction

The correct answer is: It decreases the angle of diffraction

In a diffraction grating experiment, the angle of diffraction is influenced by the wavelength of the light used. When the wavelength of light decreases, the relationship defined by the grating equation, \(d \sin(\theta) = n\lambda\), comes into play. Here, \(d\) is the distance between grating lines, \(\theta\) is the angle of diffraction, \(n\) is the order of the diffracted light, and \(\lambda\) is the wavelength. As you reduce the wavelength \(\lambda\), to maintain equality in the equation for a given value of \(d\) and \(n\), the sine of the angle \(\theta\) must also decrease. This leads to a smaller angle of diffraction. Therefore, decreasing the wavelength results in a decrease in the angle at which the light is diffracted. The other options do not hold true under the principles of diffraction: - A statement suggesting that increasing the angle of diffraction would occur contradicts the fundamental relationships in the diffraction equation. - Saying that there is no effect on the angle of diffraction overlooks the direct correlation established by the grating equation. - The notion that the direction of diffraction could reverse is not consistent with how