# CATHODE RAYS AND CATHODE RAY TUBE REVISION QUESTIONS

CATHODE RAYS AND CATHODE RAY TUBE

1. State two differences between the cathode ray tube (CRT) of a T.V and the cathode ray oscilloscope (CRO)
2. Distinguish between a photon and a quantum.
3. How does the energy of ultra violet light compare to that of yellow light given that the energy E of a wave frequency f, is given by E = hf, where h is plank’s constant?
4. A photon has energy of 5×10-19 Calculate the wavelength associated with this photon.
5. The control grid in a cathode Ray Oscilloscope (CRO) is used to control brightness of the beam on the screen. How is this achieved?
6. a) Figure 14 shows the features of a cathode ray tube.

1. i) Name the parts labelled A and B.
2. ii) Explain how the electrons are produced in tube.

iii)       State two functions of the anodes.

1. iv) At what part of the cathode ray tube would the time base be connected?
2. v) Why is a vacuum created in the tube?
3. vi) The potential between the anode and the cathode of an x-ray tube is 80kV. Calculate:
4. the energy of an electron accelerated in the tube
5. the velocity of an electron in the tube. (take electron charge e = 1.6 x 10-19C and mass of an electron = 9.11 x 10-31 kg
6. b) The graph in Figure 15 was obtained on a cathode ray oscilloscope (CRO) screen when the output of an a.c generator was connected to the input of the CRO. The time-base calibration of the CRP was set at 20 milliseconds per centimeter and the y- gain at 5 volts per centimeter.

1. i) Determine the pick voltage of the generator.
2. ii) Determine the frequency of the voltage.

iii)       On the same grid, redraw the graph for the same voltage when the time base calibration is set at 40 milliseconds per centimeter and the 7-gain at 10volts per centimeter. (Show at least one complete cycle)

1. Sketch the picture seen on the screen of a cathode ray oscilloscope when the oscilloscope is adjusted so that the spot is in the middle of the screen and the output terminals from a transformer connected to the mains are connected across the Y-plates.
2. The diagram shows the screen of a cathode ray tube, and behind it the position of the X and y plates which deflect the electron beam. The beam forms a spot on the screen.

1. a) Draw a labelled diagram showing a side view of the cathode ray tube.
2. b) How is the brightness of the spot controlled?
3. c) The “X-shift” control on the front of the cathode ray oscilloscope moves the spot sideways on the screen. What kind of voltage direct, alternating or zero) does it apply to:
4. i) The X plates
5. ii) The Y plates

The ‘time–base’ voltage normally applied to the X-plates in a RCO varies with

time as shown.

1. i) Describe the motion of the spot when the time-base is on.

1. ii) Illustrate on the diagram above what is seen on the screen if an alternating voltage is applied to the Y-plates with the time-base on.

State two uses of the CRO.

1. The control grid in a cathode ray oscilloscope (CRO) is used to control the brightness of the beam on the screen. Explain how this is achieved.
2. State and explain three uses of main parts of a CRT in an oscilloscope.
3. The figure shows the main features of cathode ray oscilloscope (C.R.O).

(a) (i) Name the parts labelled A and B.

(ii) State the function of B and briefly outline how it works.

(iii) State two function of the anodes.

• The output of an a.c generator was connected to the input of the cathode ray oscilloscope whose time base setting was 5 milliseconds per centimeter and the y-gain at 10 volts per centimeter, the figure below shows the waveform displayed on the screen of the C.R.O.

Determine

(i) The peak voltage of the generator.

(ii) The frequency of the voltage.

1. (a) The figure below shows the cathode ray oscilloscope.

• Name the parts labeled: A ,B,C and D
• Describe how the electrons are produced in the tube.
• State and explain the functions of the parts A, B and D
• State and explain what will be observed on the screen if an a.c voltage is connected across the y-plates
• State how the deflection system of a television set differs from that of a CRO
• Give reasons why it is possible to have a wider screen on the television than on the CRO
• State one use of a CRO
• State and explain the functions of the high voltage between the cathode and the anode in the tube of x-ray tube.
• State one similarity and one difference between the cathode rays and x-rays

• What are (i) the frequency and (ii) the amplitude of the signal shown in the figure below?

Time base = 50us cm-1

1. Frequency:
2. Amplitude:

• Name
• A suitable substance for coating inside the screen.
• Give two uses of a C.R.O.
1. The figure below shows a simple cathode ray tube.
• Explain how the electrons are produced in the tube.
• State one function of the anode.
• At what part of the cathode ray tube would the time base be connected? )
• Why is a vacuum created in the tube?
1. Figure 13 shows a simple cathode ray tube with only the Y-plate deflectors.

(a)  State the effect on the fluorescent spot if:

(i)  Temperature of the filament of the electron gun is raised.

(ii)  The deflector plate Y1 was positively charged while Y2 was negatively charged.

(b)             X-rays are produced when cathode rays are suddenly stopped in an x-ray tube. State how you would increase:

(i)  The intensity of x-rays produced.

(ii) The energy (strength) of X-rays produced

• Electrons are emitted from a metal surface when illuminated with suitable electromagnetic radiation. A graph of frequency (f) of radiation against maximum kinetic energy (K.E) of photoelectrons is shown.

Determine from the graph:

(i)   The threshold frequency.

(ii)  The work function of the metal.

(iii) The Plank’s constant.

(d)             Ultra-violet radiation is directed onto the zinc plate of a positively charged electroscope.

State and explain the observations made on the divergence of the leaf of the electroscope.

1. The control grids in a cathode Ray Oscilloscope (CRO) is used to control the brightness of the beam on the screen. How is this achieved?
2. State two differences between the cathode ray tube (CRT) of a TV and the cathode ray
3. A narrow beam of electrons in a cathode ray oscilloscope (CRO) strike the screen producing a spot. State what is observed on the screen if a low frequency a.c source is connected across the y-input of the CRO
4. (a) Figure 1 shows the features of a cathode ray tube

(i) Name the parts labeled A and B.

(ii) Explain how the electrons are produced in the tube.

(iii) State two functions of the anodes.

(iv) At what part of the cathode ray tube would the time be connected?

(v) Why is a vacuum created in the tube?

1. The graph in figure 2 was obtained on a cathode ray oscilloscope (CRO) screen when the output of an a.c generator was connected to the input of the CRO. The time- base calibration of the CRO was set at 20 milliseconds per centimeter and the y- gain at 5 volts centimeter.

(i) Determine the pick voltage of the generator.

(ii) Determine the frequency of the voltage.

On the same grid, redraw the graph for the same voltage when the time base calibration is set at 40 milliseconds per centimeter and y- gain at 10 volts per centimeter. (Show at least one complete cycle)

1. Figure below shows the main features of a cathode ray oscilloscope (CRO)

(i)        Name the parts labeled B and N.

B…………………………

N…………………………

(ii)       Explain how electrons are produced in the tube.

(iii)      When using the CRO to display waveforms of voltages, state where the following should be connected:-

1. The voltage to be displayed on the screen.
2. The time base voltage.
3. The figure 10 shows the waveform of voltage displayed on the screen of a CRO. The y- gain calibration was 5v per cm.

(I)        Determine the peak to peak voltage of the y- input.

(II)       Sketch on the same figure the appearance of the waveform after the voltage of the input signal I halved and its frequency is double

1. a) The figure below shows the features of a cathode ray tube
2. i) Name the parts labeled A and B.

A         ……………………

B         ……………………

1. ii) Explain how electrons are produced in the tube.

iii)       State two functions of the anodes.

1. iv) State the part where the time base would be connected.
2. v) State any two adjustments that would be made on the C.R.T to create an x-ray tub
3. b) The time base calibration of the C.R.O was set at 20milliseconds per centimeters and they gain at 5 volts per centimeter. If an a.c signal input produced a wave whose peak voltage was 20V, how many centimeters did it rise.
4. c) Give a reason why a T.V screen is wider and the tube is shorter than a C.R.O.
5. Figure below shows the main features of cathode ray oscilloscope (C.R.O)

1. (i) Name the parts labeled A and B.

(ii)State the function of B and briefly outline how it works.

(iii) State two function of the anodes.

1. What is the advantage of using the indirectly heated cathode as in figure above to the directly heated cathode?
2. State the three advantages of the above device over voltmeter.
3. The output of an a.c generator was connected to the input of the cathode ray oscilloscope whose time base settling was 5 milliseconds per centimetre and the y-gain at 10 volts per centimetre, the figure below shows the waveform displayed on the screen of the C.R.O.

Determine

• The park voltage of the generator.
• The frequency of the voltage
1. a) The figure below shows the cathode ray oscilloscope. Name the parts labelled

A…………………………………….

C…………………………………….

G……………………………………

F……………………………………

 Time base=50µs cm-1

(b) What are (a) the frequency and (b) the amplitude of the signal shown in the figure below.

(c) Name

(i) A suitable substance for coating inside the screen

(ii) Give two uses of a C.R.O

1. c) The figure below shows the trace on the screen of an a.c signal connected to the y-plates of C.R.O with time base on.

Given that the time control is 5ms/div, and the y-again is at 100V/div, determine:

1. i) The frequency of the a.c signal.
2. ii) The peak voltage of the input signal
3. d) State the importance of the magnetic coils in a television tube
4. (a) A TV tube uses a voltage of 4550V to accelerate electrons released from its cathode by      thermionic emission.

(i) What is meant by thermionic emission?

(ii) How is thermionic emission is achieved in the CRT.

(b)       Figure (a) and (b) show the screen y – gain and time base controls from a typical             oscilloscope displaying a waveform.

Screen                                                             Screen

(i) What is the setting of the y – gain control?

(ii) What is the peak voltage of the waveform?

(iii) State the time base setting

(iv) From the display waveform, state the period of the trace.

(v) Calculate the frequency of the waveform.

Figure 8

The screen of a cathode ray oscilloscope displays the trace shown in fig. 8 above. The y-sensitivity is set at 10v/cm and the time base set at 0.2ms/cm. Obtain values for:

(a) The peak voltage

(b) The frequency of the alternating signal

(c) State reasons why a C.R.O is advantageous to use as a voltmeter over ordinary meters.

(d) List two uses of the graphite used in the TV set.

1. Explain why the cathode of a CRO is coated with oxides of metals such as barium and strontium.
2. The figure below is a sketch of the time –base voltage.

State what happens to the spot along sections

1. AB
2. BC
3. The diagram below shows cathode rays thrust into a magnetic field.

1. Complete the diagram to show the path of the cathode ray
2. Magnetic fields are preferred to electric fields in the deflection system of a television tube. Explain.
3. What is the function of the following parts of a cathode ray oscilloscope?
1. The grid
2. The anode plate
• The screen
1. State the factors considered when choosing the materials for the
1. Filament
2. Cathode.
2. Describe two advantages of using a CRO in measuring voltage.
3. i) Explain why the tube of a cathode ray oscilloscope is made of thick glass walls.
4. ii) The figure shows an AC voltage on a CRO screen.

Determine the peak voltage given that the sensitivity of the vertical axis is 8V/cm.

1. The figure below shows the trace of a signal on CRO.

Given that the time base is set at 100ms/div., determine the frequency of the signal.

1. (a) The figure below shows the cathode ray oscilloscope. Name the parts labelled

A…………………………………….

C…………………………………….

G……………………………………

F……………………………………

 Time base=50µs cm-1

(b) What are (a) the frequency and (b) the amplitude of the signal shown in the figure below.

(c) Name

(i) A suitable substance for coating inside the screen

(ii) Give two uses of a C.R.O

1. a) (i) With a well labelled diagram shows how a junction diode is formed

(ii) Explain why a junction diode only conducts in one way

1. b) (i) State what is meant by breakdown voltage for a diode

(ii) Name two applications of a junction diode

1. c) The figure 8 below shows the trace on the screen of an a.c signal connected to the y-plates of C.R.O with time base on.

Given that the time control is 5ms/div, and the y-again is at 100V/div, determine:

1. i) The frequency of the a.c signal.
2. ii) The peak voltage of the input signal
3. d) State the importance of the magnetic coils in a television tube

A cathode-ray oscilloscope is adjusted so that the time for the electron beam to make one traverse of the screen from P to Q is 1/100 of a second and the Y – plate sensitivity is 1cm represents 15V. The trace on the screen is then as in fig. (a), fig. (b) and (c) shows the trace obtained when the C.R.O. is connected in turn to two voltage sources A and B.

(i)        What type of voltage sources are A and B?

(ii)       What is the voltage of B and the peak voltage of A?

(iii)      What is the frequency of source A?

1. (a) Figure 7 shows the features of a cathode ray tube

(i)        Name the parts labeled A and B

A……………………………………………………………………………

B……………………………………………………………………………

(ii)       Explain how the electrons are produced in the tube

(iii)      At what point of the cathode ray tube would the time base be connected

(iv)      State two function of the anodes

(b)       (i)        Explain how x – rays are produced

(ii)       State the functions of the high voltage between the cathode and the anode in the x – ray tube

(c)       State one similarity and one difference between cathode rays and x – rays

1. a) Study the figure  below and answer the questions that follow

1. Name the device in figure above and state one of its application
2. Name the parts of the device marked P, Q and R and the function of each part
• What is the advantage of using the indirectly heated cathode as in the figure above to the directly heated cathode
1. b) State three advantages of the above device over voltmeter
1. The figure below shows a cathode ray beam entering a magnetic field, perpendicular to the plane of the paper? Complete the diagram to show the path of the beam in the field.

The screen of a cathode ray oscilloscope displays the trace shown in fig. above. The y-sensitivity is set at 10v/cm and the time base set at 0.2ms/cm. Obtain values for:

• The peak voltage
• The frequency of the alternating signal
• State reasons why a C.R.O is advantageous to use as a voltmeter over ordinary meters.

(d) List two uses of the graphite used in the TV set.

1. The fig. below represents a cathode ray oscilloscope (C.R.O).
 D
 C
 B
 A

 Screen
 Screen

(a) (i) Name the parts labeled A and B.

A……………………………………………………………………………

B……………………………………………………………………

(ii) What are the functions of parts labeled C and D.

(iii) Explain how electrons are produced.

(iv)  Give a reason why the tube is evacuated.

(b) Four 40W bulb, and six 100W bulbs were switched on for 5 hours a day for domestic use in a certain institution. Find the monthly bill for the consumer given that the cost of electricity in the country is at 5.50 per unit (Take 1 month=30 days and standing charge of shs.150/=

(c) Give one advantage of high voltage transmission over long distances.

1. The figure below shows the features of a cathode ray oscilloscope

(a) Name the parts A and B and state the role played by each of the parts A and B

A ……………………………………………………………………………

B   ……………………………………………………………………………

(b) Explain how electrons are produced.

(c) Explain why the cathode of a C.R.O is coated with oxides of Barium and strontium

(d) The figure below shows an A.C voltage on a C.R.O screen

(e) Determine the peak voltage of the input signal given that the sensitivity of the vertical axis is 12V/cm.

(f) Give a reason why it’s possible to have a wider screen on the T.V set than on the C.R.O

• The figure below represents a cathode ray beam passing between pole pieces of a permanent magnet

 N       S

(i)Describe the path followed by the beam and give reason for your answer.

(ii) Show the direction of current on the figure

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