Discovery Of The Electron - William Crookes

Question 1

What did William Crookes discover?

Answer 1

Cathode rays

Question 2

Who discovered cathode rays?

Answer 2

William Crookes

Question 3

What experiment did Crookes carry out first?

Answer 3

He carried out an experiment to investigate what happens when an electric current is passed through a glass tube containing air at low pressure

Question 4

What is the glass used by Crookes commonly called?

Answer 4

A vacuum tube

Question 5

When carrying out his experiment, what did Crookes find?

Answer 5

He found that radiation was coming from the metal plate inside the tube connected to the negative end of the power supply

Question 6

Describe the apparatus used by Crooks in his first experiment
(4)

Answer 6

A vacuum tube containing a Maltese cross

The Maltese cross found in the middle of the tube is connected to the positive end of a power supply (anode)

A metal plate at the small end of the vacuum tube is connected to the negative end of the power source (cathode)

Shadow of the Maltese cross appears on the opposite side of the vacuum tube to the cathode

Question 7

What is the negative plate inside the vacuum tube called?

Answer 7

The cathode

Question 8

What is the positive cross inside the vacuum tube called?

Answer 8

The anode

Question 9

What was formed at the other end of the tube from the cathode?

Answer 9

A shadow of the Maltese cross

Question 10

What is placed in the middle of the vacuum tube?

Answer 10

A Maltese cross

Question 11

What name did Crookes use to describe the rays coming from the cathode?

Answer 11

Cathode rays

Question 12

What happens when the cathode rays strike the glass?

Answer 12

The cathode rays themselves are invisible but they cause the glass to glow or fluoresce

Question 13

What causes the shadow?

Answer 13

The cathode rays being stopped by the Maltese cross

Question 14

Why did Crookes carry out a second experiment?

Answer 14

To investigate the properties of cathode rays

Question 15

Describe Crookes’ second experiment

Answer 15

He placed a light paddle wheel, mounted on rails in front of the cathode

Question 16

What did Crookes discover when the current was switched on during his second experiment?

Answer 16

He found that the paddle wheel rotated and travelled down the tube

Question 17

During his second experiment. what did Crookes put in front of the cathode?

Answer 17

He put a light paddle wheel, mounted on rails in front

Question 18

During his second experiment, what did Crookes mount the light paddle wheel on?

Answer 18

On rails

Question 19

During his second experiment, what did Crookes notice when the paddle wheel began to spin?

Answer 19

He noticed that the vanes always turned away from the cathode

Question 20

What did Crookes conclude from his second experiment?

Answer 20

He concluded that the vanes were being struck by particles coming from the cathode

Question 21

What three deductions did Crookes make from his two experiments?
(3)

Answer 21

Cathode rays travel in straight lines (shadow of cross was sharp)

Cathode rays cause glass to fluoresce when they strike it

Cathode rays posses enough energy to move a paddle wheel

Question 22

Why could Crookes deduct that the cathode rays travelled in a straight line?

Answer 22

Because the shadow of the Maltese cross was sharp

Question 23

What do cathode rays cause to fluoresce?

Answer 23

Glass

Question 24

How much energy do cathode rays have?

Answer 24

Enough to move a paddle wheel