Chapter 6 · X-rays: practice questions

A narrow beam of X-rays is passed through a strong magnetic field, but the beam suffers no deflection. This shows that X-rays...

• Aconsist of a stream of positive ions.
• Bhave an extremely long wavelength.
• Ctravel much more slowly than visible light.
• Dcarry no electric charge, being electromagnetic waves.

In a Coolidge tube used to produce X-rays, the X-rays are emitted when...

• Avisible light is reflected from the polished anode.
• Ba beam of protons is fired at the cathode.
• Cthe metal filament is heated until it glows.
• Da beam of high-speed electrons is suddenly decelerated on striking a metal target.

The wavelengths of the lines of the characteristic X-ray spectrum of a Coolidge tube depend on...

• Athe material of the target (anode).
• Bthe temperature of the filament.
• Cthe number of electrons emitted by the filament.
• Dthe overall length of the tube.

The continuous X-ray spectrum produced by a Coolidge tube originates from...

• Athe thermal glow of the heated filament.
• Bthe deceleration of the bombarding electrons within the target.
• Cthe ionisation of residual gas molecules inside the tube.
• Delectron transitions between the inner energy levels of the target atoms.

All of the following are practical uses of X-rays EXCEPT...

• Adetecting hidden cracks (flaws) inside metal castings.
• Btreating certain cancerous tumours.
• Cstudying the arrangement of atoms in crystals by diffraction.
• Damplifying an electric current in a transistor circuit.

When the accelerating potential difference between the cathode and the target of a Coolidge tube is increased, the shortest wavelength of the continuous X-ray spectrum...

• Adecreases.
• Bincreases.
• Cfirst increases then remains constant.
• Dremains constant.

In a Coolidge tube, the filament current is increased while the accelerating potential difference is kept constant. What happens to the intensity of the X-rays and to the shortest wavelength of the continuous spectrum, respectively?

• AIntensity increases ; shortest wavelength decreases.
• BIntensity remains constant ; shortest wavelength increases.
• CIntensity increases ; shortest wavelength remains constant.
• DIntensity decreases ; shortest wavelength decreases.

A Coolidge tube is operated at a potential difference of 50 kV. The shortest wavelength of the continuous X-ray spectrum it produces is approximately (h = 6.6×10⁻³⁴ J·s, c = 3×10⁸ m/s, e = 1.6×10⁻¹⁹ C)...

• A4.0×10⁻¹¹ metre
• B2.5×10⁻¹¹ metre
• C2.5×10⁻¹³ metre
• D2.5×10⁻⁹ metre