shows an apparatus used to measure the distribution of the speeds of gas molecul
ID: 2018086 • Letter: S
Question
shows an apparatus used to measure the distribution of the speeds of gas molecules. The device consists of two slotted rotating disks separated by a distance d, with the slots displaced by the angle . Suppose the speed of light is measured by sending a light beam toward the left disk of this apparatus.
(a) Show that a light beam will be seen in the detector (that is, will make it through both slots) only if its speed is given by c = d/, where is the angular speed of the disks and is measured in radians.
(b) What is the measured speed of light if the distance between the two slotted rotating disks is 2.500 m, the slot in the second disk is displaced 1/60 of 1 degree from the slot in the first disk, and the disks are rotating at 5552 rev/s?
m/s
Explanation / Answer
From given data separation between two plates is d speed of the light is c time taken to travel a distance d is t = d / c ---------------(1) The angular velocity of the disk is = / t t = / ------------- (2) From equations (1) and (2) we get d / c = / c = d / (b) separation between two disks is d = 2.500 m angle is = (1/60) degrees = (1/60) degrees (1 rev / 360 degrees) = 4.629x10-5 rev = 4.629x10-5 rev Angular velocity is = 5552 rev/s Then the speed of light is c = 5552 rev/s * 2.50m / 4.629x10-5 rev = 299808000 m/s = 2.99x108 m/sRelated Questions
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