Home
Class 12
PHYSICS
The mean free path of the electrons in a...

The mean free path of the electrons in a discharge tube is 20 cm. The tube itself is 10cm long. What is the length of the Crookes dark space?

Text Solution

Verified by Experts

The mean free path of the electrons is much longer than the length of the tube. Thus, the electrons, in general, do not collide in between, no ionization takes place and hence no light is emitted. The crookes dark space fills the entire tube and hence is 10cm long.
Promotional Banner

Topper's Solved these Questions

  • ELECTRIC CURRENT THROUGH GASES

    HC VERMA|Exercise Short Answer|10 Videos

  • ELECTRIC CURRENT THROUGH GASES

    HC VERMA|Exercise Objective 1|9 Videos

  • ELECTRIC CURRENT THROUGH GASES

    HC VERMA|Exercise Exercises|23 Videos

  • ELECTRIC CURRENT IN CONDUCTORS

    HC VERMA|Exercise Exercises|84 Videos

  • ELECTRIC FIELD AND POTENTIAL

    HC VERMA|Exercise Exercises|75 Videos

Similar Questions

Explore conceptually related problems

An electron gun with its collector at a potential of 100 v fires out electrons in a spherical bulb containing hydrogen gas at low pressure (~10^(-2)" mm of Hg") . A magnetic field of 2.83 xx 10^(-4) T curves the path of the electrons in a circular orbit of radius 12.0 cm. (The path can be viewed because the gas ions in the path focus the beam by attracting electrons, and emitting light by electron capture, this method is known as the ‘fine beam tube’ method.) Determine e/m from the data.

An open glass tube is immersed in mercury in such a way that a length of 8 cm extends above the mercury level. The open end of the tube is then closed and sealed and the tube is raised vertically up by additional 46 cm. what will be length of the air column above mercury in the above now ? (Atmospheric pressure = 76 cm of Hg)

The first resonance length of a resonance tube is 40 cm and the second resonance length is 122 cm . The third resonance length of the tube will be

Two 20g worms climb over a 10cm high, very then wall. One worm is thin and 20cm long the other is fat and only 10cm long. What is the ratio of the potential energy (w.r.t. the base of wall) of the thin worm as comparses to that of the fat worm when each is half way over the top of the wall as shown?

Water rises to a height of 10cm in a glass capillary tube. If the area of cross section of the tube is reduced to one fourth of the former value what is the height of water rise now?

A point source of light is kept at a distance of 15cm from a converging lens,on its optical axis.The focal length of the lens is 10cm and its diameter is 3cm ,A screen is placed on the other side of the lens ,perpendicular to the axis of lens,at a distance 20cm from it.Then find the area of the illuminated part of the screen?

A barometer is faulty . When the true barometer reading are 73 cm and 75 cm of Hg , the faulty barometer reads 69 cm and 70 cm respectively (i) What is the total length of the barometer tube? (ii) What is the reading when the faulty barometer reads 69.5 cm? (iii) What is the faulty barometer reading when the true barometer reads 74 cm?

The external diameter of a 314 m long copper tube is 1.2 cm and the internal diameter is 1 cm. calculate its resistance if the specific resistance of copper is 2.2xx10^(-8) ohm-metre.

Vibrating tuning fork of frequency n is placed near the open end of a long cylindrical tube. The tube has a side opening and is fitted with a movable reflecting piston. As the piston is moved through 8.75 cm , the intensity of sound changes from a maximum to minimum. If the speed of sound is 350 m//s . Then n is