Join
Topic

X-rays

Estimated reading: 4 minutes 728 views Contributors

What are X-rays?

– X-rays were discovered by a German scientist namedRoentgen in 1985.
– They can pass through most substances including soft tissues of the body but not through bones and most metals.
– They were named X-rays meaning ‘unknown rays’.
X-ray-phy Form Four

X-ray Production

– They are produced by modified discharge tubes called X-ray tubes.
– The cathode is in the form of a filament which emits electrons on heating.
– The anode is made of solid copper molybdenum and is called the target.
– A high potential difference between the anode and the cathode is maintained (10,000 v to 1,000,000 or more) by an external source.
– The filament is made up of tungsten and coiled to provide high resistance to the current. The electrons produced are changed into x-rays on hitting the anode and getting stopped. Only 0.2% of the energy is converted into x-rays. – Cooling oil is led in and out of the hollow of the anode to maintain low temperature. The lead shield absorbs stray x-rays.
X-ray production-phy Form Four

Energy changes in an X-ray tube

– When the cathode is heated electrons are emitted by thermionic emission. They acquire electrical energy which can be expressed as E = e V. – Once in motion the electrical energy is converted to kinetic energy, that is eV =½ me v2.
– The energy of an electromagnetic wave can be calculated using the following equation:
Energy = h f, where h – Planck’s constant, f – frequency of the wave.

– The highest frequency of the X-rays released after an electron hits the target is when the greatest kinetic energy is lost, that is h f max = eV.
– Lower frequencies are released when the electrons make multiple collisions losing energy in stages, the minimum wavelength, λ min, of the emitted X-rays is given by; (hc) / λ min = eV.
These expressions can be used to calculate the energy, frequencies and wavelengths of X-rays.

1. Determine the energy possessed by X-rays whose frequency is 4 × 1017 Hz.

Solution
E = h f => 6.63 × 10-34 ×4 × 1017 = 2.652 × 10-16 J.

2. An x-ray tube operates at 60 kV and the current through it is 4.0 mA. Calculate the:
a) Number of electrons striking the target per second.
b) Speed of the electrons when they hit the target

Solution-phy Form Four

3. An 18 kV accelerating voltage is applied across an X-ray tube. Calculate:
a) The velocity of the fastest electron striking the target
b) The minimum wavelength in the continuous spectrum of X-rays produced. (mass of electron – 9 × 10-31 kg, charge on an electron-1.6 × 10-19 C, h- 6.6 × 10-34 J/s, c – 3 × 108 m/s)

Solution-phy Form Four

Properties of X-rays

  1. They travel in straight lines
  2. They undergo reflection and diffraction
  3. They are not affected by electric or magnetic fields since they are not charged particles.
  4. They ionize gases causing them to conduct electricity
  5. They affect photographic films
  6. They are highly penetrating, able to pass easily through thin sheets of paper, metal
  7. They are highly penetrating, able to pass easily through thin sheets of paper, metal foils and body tissues
  8. They cause fluorescence in certain substances for example barium platinocynide.

Hard X-rays

These are x-rays on the lower end of their range (10-11 – 10-8 m) and have more penetrating power than normal x-rays. They are capable of penetrating flesh but are absorbed by bones.

Soft X-rays

They are on the upper end of the range and are less penetrative. They can only penetrate soft flesh and can be used to show malignant growth in tissues.

Dangers of X-rays and the precautions.

  1. They can destroy or damage living cells when over exposed.
  2. Excessive exposure of living cells can lead to genetic mutation.
  3. As a precautionary measure X-ray tubes are shielded by lead shields.

Uses of X-rays

1. Medicine – X-ray photos called radiographs are used as diagnostic tools for various diseases. They are also used to treat cancer in radiotherapy.
2. Industry – They are used to photograph and reveal hidden flaws i.e. cracks in metal casting and welded joints.
3. Science – Since the spacing of atomic arrangement causes diffraction of x-rays then their structure can be studied through a process called X-ray crystallography.
4. Security – Used in military and airport installations to detect dangerous metallic objects i.e. guns, explosives, grenades etc.

X-rays - PreviousCathode Rays and Cathode Ray TubeNext - X-raysPhotoelectric Effect

Related articles

Leave a Comment

Share this Doc

X-rays

Or copy link

CONTENTS

Made with ❤️ by Darasa Huru

Learning BaseContact

Download Form Six General Chemistry Book (New Syllabus PDF)

Gain a commanding grasp of molecular characteristics, chemical structures, and t

Form Six General and Inorganic Chemistry Book PDF -TIE New Syllabus

Gain a commanding grasp of elemental characteristics, periodic patterns, and che

Download Form Five General and Inorganic Chemistry Book (TIE New Syllabus PDF)

Master the foundational behaviors, structural trends, and reaction mechanisms of

Form Five General Chemistry Book PDF- TIE New Syllabus

Master the essential theories of molecular structures and properties with the Fo

Download Form Five and Six Physical Chemistry Book (TIE New Syllabus)

Conquer the demanding mathematical frameworks and structural laws of chemical sy

Download Form Five and Six Physical Chemistry Book (TIE New Syllabus)

Master the intricate math and fundamental behaviors of matter with the Form Five

Form 5 and 6 Inorganic Chemistry Book PDF (TIE New Syllabus)

Enhance your comprehension of advanced chemical principles with the Form 5 and 6

Form Five and Six Organic Chemistry Book-TIE New Syllabus

Conquer the demanding hurdles of A-Level carbon chemistry with the Form Five and

Download Form Five and Six Inorganic Chemistry Book (TIE New Syllabus)

Deepen your grasp of advanced chemical principles with the Form Five and Six Ino

Form Five and Six Organic Chemistry Book PDF-TIE New Syllabus

Master the complexities of Advanced Level organic chemistry with the Form Five a

Form Six Chemistry

If Form Five was about laying the foundation of Advanced Level (A-Level) chemist

Form Five Chemistry

Transitioning from O-Level to A-Level chemistry is a massive step. Form Five Che

Chat Icon Close Icon

Subscribe

×
Cancel