A laser producing red light of wavelength 655 nm is directed onto double slits separated by a distance, `d=5.0 xx 10^{-5} \ text{m}`. A screen is placed behind the double slits.
- Newton proposed a model of light. Use a labelled sketch to show the pattern on the screen that would be expected from Newton's proposed model. (2 marks)
- When the laser light is turned on, a series of vertical bright lines are seen on the screen.
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- Calculate the angle, `\theta`, between the centre line and the bright line at `A`. (3 marks)
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- The laser is replaced with one producing green light of wavelength 520 nm.
- Explain the difference in the pattern that would be produced. (2 marks)
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a.
b. `theta=1.50^@`
c. Consider `d sin theta = m lambda :`
→ `sin theta prop lambda`
→ Using light with a shorter wavelength decreases the angular separation of bright fringes.
→ The bright lines will appear closer together.
b. Using `d sin theta=mlambda:`
| `5.0 xx10^(-5) sin theta` | `=2 xx6.55xx10^(-7)` |
| `sin theta` | `=(2 xx6.55xx10^(-7))/(5.0 xx10^(-5))` |
| `theta` | `=1.50^@` |
c. Consider `d sin theta = m lambda :`
→ `sin theta prop lambda`
→ Using light with a shorter wavelength decreases the angular separation of bright fringes.
→ The bright lines will appear closer together.
