QUESTION 8 [6 marks]

Question

An experiment is set up to determine the relationship between the degree of diffraction and the wavelength of light. Monochromatic red light shines through a slit with a width of 0,04 mm and a pattern is produced on a screen.
Figure 12: Diagram showing a monochromatic light ray through a slit.
Question 8.1 [2 marks] Define Huygen’s principle.
18

Question 8.2
The slit width for the same light is changed various times throughout the experiment and the results are recorded below:
Figure 13: Graph of degree of diffraction vs slit width.
Question 8.2.1 [1 mark]
What is the independent variable for this experiment?
Question 8.2.2 [1 mark]
What is the one factor that needs to be constant for this experiment? Question 8.2.3 [2 marks]
Write down a conclusion for this experiment.

Answer 1

Question 8.1:
Huygen's principle states that every point on a wavefront can be considered as a source of secondary wavelets that spread out in all directions at the speed of light.

Question 8.2.1:
The independent variable for this experiment is the slit width.

Question 8.2.2:
The one factor that needs to be constant for this experiment is the wavelength of the monochromatic red light.

Question 8.2.3:
Based on the results recorded in Figure 13, it can be concluded that there is a direct relationship between the degree of diffraction and the slit width. As the slit width increases, the degree of diffraction also increases. This demonstrates the phenomenon of diffraction, where light waves bend around obstacles and spread out when passing through narrow openings.