Light of wavelength 490 nm is incident on a narrow slit. The diffraction pattern is viewed on a screen \(3.20 \mathrm{m}\) from the slit. The distance on the screen between the central maximum and the third minimum is $2.5 \mathrm{cm} .$ What is the width of the slit?

Short Answer

Expert verified
Answer: The width of the slit is approximately 3.22 µm.

Step by step solution

01

Identify the given information

The given information in the problem is as follows: - Wavelength of light (\(\lambda\)): \(490\,\mathrm{nm}\) - Distance between the slit and the screen (L): \(3.20\,\mathrm{m}\) - Distance on the screen between the central maximum and the third minimum (y): \(2.5\,\mathrm{cm}\) Keep in mind that we need to convert the given distances to the same unit (meters).
02

Convert the distances to meters

Convert the distances to meters using the following conversions: - \(\lambda = 490\,\mathrm{nm} \times 10^{-9}\,\frac{\mathrm{m}}{\mathrm{nm}} = 490 \times 10^{-9}\,\mathrm{m}\) - \(y = 2.5\,\mathrm{cm} \times 10^{-2}\,\frac{\mathrm{m}}{\mathrm{cm}} = 2.5 \times 10^{-2}\,\mathrm{m}\) Now, we have \(\lambda = 490 \times 10^{-9}\,\mathrm{m}\), L = \(3.20\,\mathrm{m}\), and y = \(2.5 \times 10^{-2}\,\mathrm{m}\).
03

Use the formula for the angular position of the minima

The formula for the angular position of the minima in a single-slit diffraction pattern is given by: $$ m\lambda = a\sin\theta $$ where: - m is the order of the minimum (m = 3 for the third minimum) - a is the width of the slit - \(\theta\) is the angle between the central maximum and the minimum First, we need to find the angle \(\theta\).
04

Calculate the angle θ

Use the geometry of the situation to calculate the angle \(\theta\). In this case, the slit is the adjacent side, y is the opposite side of the right triangle, and L is the hypotenuse. Therefore, we have: $$ \tan\theta = \frac{y}{L} \Rightarrow \theta = \arctan{\frac{y}{L}} $$ Plugging in the values for y and L, we get: $$ \theta = \arctan{\frac{2.5 \times 10^{-2}\,\mathrm{m}}{3.20\,\mathrm{m}}} \approx 0.449\,\mathrm{rad} $$
05

Substitute the values into the formula for minima and solve for a

Now we are ready to substitute the values into the formula to find the width of the slit (a). For the third minimum, m = 3. We have: $$ 3(490 \times 10^{-9}\,\mathrm{m}) = a\sin{0.449\,\mathrm{rad}} $$ Solve for a: $$ a = \frac{3(490 \times 10^{-9}\,\mathrm{m})}{\sin{0.449\,\mathrm{rad}}} \approx 3.22 \times 10^{-6}\,\mathrm{m} $$
06

Convert the width of the slit to micrometers and present the final answer

Convert the width of the slit from meters to micrometers: $$ a = 3.22 \times 10^{-6}\,\mathrm{m} \times 10^{6}\,\frac{\mathrm{\mu m}}{\mathrm{m}} \approx 3.22\,\mathrm{\mu m} $$ Hence, the width of the slit is approximately \(3.22\,\mathrm{\mu m}\).

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