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Right answer is (C) Ampoules

For EXPLANATION: LIQUID samples must be counted USING ionization chamber by PLACING them in ampoules. The ampoules are placed in the chamber.

The correct option is (b) False

To explain I would SAY: GAMMA CAMERA uses MULTIPLE scintillation detectors. Hence, it is also known as scintillation camera.

Correct answer is (b) SCINTILLATION DETECTOR

The best I can EXPLAIN: Gamma camera uses a scintillation detector to produce a position INTENSITY picture of a radioactive area. It is an IMAGING device commonly used in medical applications.

Right option is (d) Self-ABSORPTION

To explain I would say: In self-absorption, the radiation emitted by the isotope is not detected DUE to the absorption of the radiation by the SAMPLE itself. It MAY OCCUR due to precipitates.

Right CHOICE is (d) Blue

To elaborate: When UV light is absorbed by the fluor MOLECULES the light emitted is in blue colour. Light is emitted when the molecules return to the GROUND state.

The CORRECT answer is (b) NEUTRON to proton RATIO

The best explanation: The STABILITY of the nucleus can be predicted by neutron to proton ratio. The number of protons will always be equal to the number of ELECTRONS.

Right choice is (c) H-number

Easiest EXPLANATION: A quench curve can be constructed by plotting the counting EFFICIENCY versus H-number. This is done using a set of SAMPLES with known activity.

The correct option is (C) Pre-amplifier

The EXPLANATION: The unmarked COMPONENT is pre-amplifier. There are two AMPLIFIERS namely pre-amplifier and main amplifier.

Correct OPTION is (a) Rejects signals below a CERTAIN voltage

To EXPLAIN I would say: The discriminator can be set to reject signals below a certain voltage. This is required for EXCLUDING scattered radiation and noise.

The correct answer is (d) COLLISION effect

The explanation is: Upon INTERACTION with MATTER, gamma rays lose ENERGY in three modes. Compton effect occurs when a gamma ray and an ELECTRON make an elastic collision.

The correct ANSWER is (a) Alpha particles

For explanation I WOULD say: Alpha particles are highly effective in PRODUCING ION PAIRS when they pass through the matter. They have relatively large mass and charge.

Right option is (a) Collimator

To elaborate: Collimator is a pattern of holes through gamma ray absorbing material, usually LEAD or tungsten. In the CONVENTIONAL METHOD, the collimator is placed over the DETECTOR crystal.

Correct choice is (d) SCHMITT trigger

For EXPLANATION I would say: A DISCRIMINATOR CIRCUIT is a Schmitt trigger circuit. There are two discriminator circuits in PULSE height analyser.

Correct OPTION is (d) PARALLEL ARRAY of discriminators

Easy explanation: Parallel array of discriminators are used when the NUMBER of channels is ten or LESS. If the number is more than ten this is not preferred.

Right CHOICE is (a) True

To EXPLAIN: The measurement of PULSE HEIGHT is USEFUL for energy determination. This is accomplished by the pulse height analyser.

Right answer is (a) Eliminate the NEED for CHEMICAL PREPARATION

The explanation: Radiochemical METHODS eliminate the need for chemical preparation. In other methods, chemical preparation has to be done before the measurement.

Right ANSWER is (c) GAMMA particles

Explanation: Gamma particle emissions have low ionizing power. They ALSO have high penetrating power.

Correct OPTION is (d) Flame EMISSION detector

Explanation: Flame emission detector is not a TYPE of radiation detector. Radiation can be detected by several methods.

The CORRECT option is (c) COUNTER

The explanation is: The signal REACHING the counter is the ONE lying in the window of PULSE height analyser. Scalar and counter follow the anti-coincidence circuit.

Right answer is (a) True

Best explanation: Alpha emission is characteristic of heavier radioactive ELEMENTS such as thorium, uranium, ETC. They are most HARMFUL to HUMAN TISSUE.

The CORRECT option is (b) False

To explain: VARIATION of gain with temperature causes instability. There are VARIOUS other factors that CAUSE instability.

The correct answer is (d) Position CIRCUITRY

To elaborate: Position circuitry adds all the signals and determines where each scintillation event occurred in the DETECTOR. It is an electronic circuit and it receives all the signals from PHOTO MULTIPLIER TUBE.

The correct option is (a) True

The BEST explanation: If number of channels is more than ten, the problems of stability of DISCRIMINATION VOLTAGES arise. Problems also arise with an INCREASE of adequate differential non-linearity.

The CORRECT CHOICE is (a) SODIUM chloride

Explanation: Scintillation detector is a large flat CRYSTAL of sodium iodide. It is COATED with thallium doping.

The correct option is (d) DISCRIMINATORS

To EXPLAIN: The PULSES having amplitudes between the two triggering LEVELS are given by discriminators. There are two discriminators.

Right choice is (C) Photo multiplier tubes

Explanation: Collimator is the first object that an emitted gamma PHOTON ENCOUNTERS after exciting the body. In the conventional method, the collimator is PLACED over the detector crystal.

The CORRECT choice is (c) Anti-coincidence circuit

Explanation: Anti-coincidence circuit CANCELS all the PULSES which trigger both the discriminators. The output of the anti-coincidence circuit is given to counters.

Right CHOICE is (C) It should be maintained at low temperature

The best I can explain: The main disadvantage of solid state SEMICONDUCTOR detector is that it must be maintained at low temperature. This is NECESSARY to reduce noise and to prevent DETERIORATION of detector characteristics.

Correct ANSWER is (a) PHOTOELECTRIC effect

Explanation: Upon interaction with matter, gamma rays lose energy in three modes. Photoelectric effect TRANSFERS all the energy of the gamma ray to an ELECTRON in the inner orbit of the atom of the absorber.

The correct CHOICE is (b) Anger camera

Explanation: The FIRST GAMMA camera is also KNOWN as an Anger camera. It was DEVELOPED by Hal Anger.

The correct answer is (b) Argon gas

To explain I WOULD say: Argon gas acts as ionising gas in Geiger Muller COUNTER. It is present in a gas TYPE envelope ALONG with the electrodes.

Correct OPTION is (a) LOW energy beta MATERIALS

The best I can explain: LIQUID Scintillators are used for low energy beta materials. Solid scintillators are used for HIGH energy beta materials.

Right option is (b) SOLUTE

Easy explanation: In liquid scintillation counter, a MIXTURE of SOLVENT and solute is used. The solute is a fluorescent SUBSTANCE.

The CORRECT answer is (a) True

To elaborate: Photomultipliers USED in Liquid scintillation DETECTORS are a source of instability. Various factors CAUSE instability.

The correct answer is (C) Colour quenching

For explanation I would say: Scintillators emit light in the BLUE region of the SPECTRUM. Due to the presence of other COLOURS, colour quenching MAY occur.

Right option is (C) Polytetrafluoroethylene

The best I can explain: Polytetrafluoroethylene is used as the INSULATION between the inner and outer ELECTRODES of the ion CHAMBER. The material has very HIGH resistance.

The correct OPTION is (c) Dynodes

Easiest explanation: The unmarked components are dynodes. SCINTILLATION detector is a combination of scintillator and PHOTO MULTIPLIER tube.

Correct ANSWER is (c) Pre-amplifier

Best explanation: Pre-amplifier is not a COMPONENT of the gamma camera. It is an IMAGING device COMMONLY used in medical applications.