Discovery Of The Electron - William Crookes Flashcards Preview

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1

What did William Crookes discover?

Cathode rays

2

Who discovered cathode rays?

William Crookes

3

What experiment did Crookes carry out first?

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

4

What is the glass used by Crookes commonly called?

A vacuum tube

5

When carrying out his experiment, what did Crookes find?

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

6

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

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

7

What is the negative plate inside the vacuum tube called?

The cathode

8

What is the positive cross inside the vacuum tube called?

The anode

9

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

A shadow of the Maltese cross

10

What is placed in the middle of the vacuum tube?

A Maltese cross

11

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

Cathode rays

12

What happens when the cathode rays strike the glass?

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

13

What causes the shadow?

The cathode rays being stopped by the Maltese cross

14

Why did Crookes carry out a second experiment?

To investigate the properties of cathode rays

15

Describe Crookes' second experiment

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

16

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

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

17

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

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

18

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

On rails

19

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

He noticed that the vanes always turned away from the cathode

20

What did Crookes conclude from his second experiment?

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

21

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

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

22

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

Because the shadow of the Maltese cross was sharp

23

What do cathode rays cause to fluoresce?

Glass

24

How much energy do cathode rays have?

Enough to move a paddle wheel