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29b怎么做
Q29.
Figure 1 shows apparatus used to determine the wavelength of laser light using Young's double-slit method.
Figure 1
(a) Figure 2 shows the actual size of part of the interference fringe pattern seen on the screen.
Figure 2
actual size
Determine, in $\mathrm{mm}$, an accurate measurement for the fringe spacing $w$.
$w=$
$\qquad$
$287$
(b) Calculate the percentage uncertainty in your value for $w$.
percentage uncertainty $=$
(2)
(c) The distance between the slits is $0.420 \mathrm{~mm}$ with an uncertainty of $\pm 1.2 \%$. The distance from the slits to the screen is $8.40 \mathrm{~m}$ with an uncertainty of $\pm 0.6 \%$. Calculate, in $\mathrm{nm}$, the wavelength of the laser light.
wavelength $=$ $\qquad$ $\mathrm{nm}$
(2)
(d) Calculate the absolute uncertainty in your value for the wavelength.
absolute uncertainty $=$ $\qquad$ $\mathrm{nm}$
(3)
(Total 9 marks)
Q30.
An interference pattern is produced using monochromatic light from two coherent sources. The separation of the two sources is $0.25 \mathrm{~mm}$ and the fringe separation is $7.8 \mathrm{~mm}$. The interference pattern is observed on a screen that is $3.5 \mathrm{~m}$ from the sources.
(a) Calculate the wavelength of the light used to produce the interference pattern.
wavelength $\qquad$
(3)
288
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Answer from Sia

Posted 5 months ago

Answer

The percentage uncertainty in the value for $w$ is calculated using the formula for percentage uncertainty.

Solution

a

Identify the given value for fringe spacing $w$: From the provided information, $w = 287 \, \text{mm}$

b

Determine the uncertainty in the measurement of $w$: Since the problem does not provide a specific uncertainty value, we assume a typical measurement uncertainty. For example, if the uncertainty is $\pm 1 \, \text{mm}$, then the absolute uncertainty is $1 \, \text{mm}$

c

Calculate the percentage uncertainty: The formula for percentage uncertainty is given by:
$\text{Percentage uncertainty} = \left( \frac{\text{Absolute uncertainty}}{\text{Measured value}} \right) \times 100$
Substitute the values:
$\text{Percentage uncertainty} = \left( \frac{1 \, \text{mm}}{287 \, \text{mm}} \right) \times 100 \approx 0.35\%$

Key Concept

Percentage uncertainty calculation

Explanation

The percentage uncertainty is found by dividing the absolute uncertainty by the measured value and multiplying by 100.

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