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Difficulty: MediumX-rays: Production, Properties, and Applications

In a Coolidge X-ray tube, increasing the current passing through the filament increases the intensity of the emitted X-rays without altering their penetrating power (hardness).

Answer: Answer

Answer

The statement is true. Filament current controls the rate of thermionic emission (X-ray intensity), whereas accelerating voltage controls the energy and penetrating power (X-ray hardness).
The statement is correct because filament current solely regulates the rate of thermionic emission, controlling the total number of electrons striking the target per second and thus the intensity of the X-ray beam. Penetrating power (hardness) depends on the accelerating potential difference, which dictates maximum electron kinetic energy and minimum X-ray wavelength.

Step-by-Step Solution

1
Analyze the effect of increasing filament current on electron emission in an X-ray tube.
Higher filament current causes greater heating, resulting in an increased rate of thermionic emission (more electrons emitted per second).
Thermionic emission depends directly on temperature, which increases with filament heating current.
2
Relate electron emission rate to X-ray intensity.
A higher number of incident electrons per second yields a proportional increase in the number of X-ray photons emitted per second (higher intensity).
Intensity measures the energy radiated per unit area per unit time, which depends on the total photon count.
3
Evaluate the factors determining X-ray penetrating power (hardness).
Penetrating power remains constant because the accelerating voltage VV across the anode and cathode was not changed (Emax=eV=hcλminE_{\text{max}} = e V = \frac{h c}{\lambda_{\text{min}}}).
Photon energy and minimum cutoff wavelength are strictly determined by accelerating voltage, not by filament current.

Key Concept

Independence of X-ray Intensity and X-ray Hardness (Penetrating Power)
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Topics

X-rays: Production, Properties, and Applications

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