IB Physics-Theme C-Qc#15 Paper 2-Double slits-

A student investigates how light can be used to measure the speed of a toy train. Light from a laser is incident on a double slit. The light from the slits is detected by a light
sensor attached to the train.
The graph shows the variation with time of the output voltage from the light sensor as the train moves parallel to the slits. The output voltage is proportional to the intensity of light incident on the sensor.
a. Explain, with reference to the light passing through the slits, why a series of voltage peaks
occurs.
b. The slits are separated by 1.5 mm and the laser light has a wavelength of 6.3 x 10–7 m. The slits are 5.0 m from the train track. Calculate the separation between two adjacent positions of the train when the output voltage is at a maximum.
c. Estimate the speed of the train.
d. A student investigates how light can be used to measure the speed of a toy train.
Light from a laser is incident on a double slit. The light from the slits is detected by a light sensor attached to the train.
The graph shows the variation with time of the output voltage from the light sensor as the train moves parallel to the slits. The output voltage is proportional to the intensity of light incident on the sensor. As the train continues to move, the first diffraction minimum is observed when the light
sensor is at a distance of 0.13 m from the centre of the fringe pattern.
- Determine the width of one of the slits.
- Suggest the variation in the output voltage from the light sensor that will be observed as
the train moves beyond the first diffraction minimum
Topic 4 and topic 9 oscillations and waves playlist: