why do cathode rays produce X-rays on striking with tungsten?

Answer 1

Cathode rays have high energy. This energy is transformed into varities of electromagnatic rays when incident on different materials by the following formula : -

E = h*f --- --- --- --- --- (1);

(where E = energy, h = Planck's constant, f = frequency of radiation).

In the case of Cathode rays falling on tungsten, the value of 'E' is such that 'f' comes in the range of X-rays.

Different materials give different frequencies. Tungsten gives off X-rays.

Answer 2

The heart of an X-ray machine is an electrode pair -- a cathode and an anode -- that sits inside a glass vacuum tube. The cathode is a heated filament, like you might find in an older fluorescent lamp. The machine passes current through the filament, heating it up. The heat sputters electrons off of the filament surface. The positively-charged anode, a flat disc made of tungsten, draws the electrons across the tube.
The heart of an X-ray machine is an electrode pair -- a cathode and an anode -- that sits inside a glass vacuum tube. The cathode is a heated filament, like you might find in an older fluorescent lamp. The machine passes current through the filament, heating it up. The heat sputters electrons off of the filament surface. The positively-charged anode, a flat disc made of tungsten, draws the electrons across the tube.
Free electrons can also generate photons without hitting an atom. An atom's nucleus may attract a speeding electron just enough to alter its course. Like a comet whipping around the sun, the electron slows down and changes direction as it speeds past the atom. This "braking" action causes the electron to emit excess energy in the form of an X-ray photon.

The high-impact collisions involved in X-ray production generate a lot of heat. A motor rotates the anode to keep it from melting (the electron beam isn't always focused on the same area). A cool oil bath surrounding the envelope also absorbs heat.

The entire mechanism is surrounded by a thick lead shield. This keeps the X-rays from escaping in all directions. A small window in the shield lets some of the X-ray photons escape in a narrow beam. The beam passes through a series of filters on its way to the patient.

A camera on the other side of the patient records the pattern of X-ray light that passes all the way through the patient's body. The X-ray camera uses the same film technology as an ordinary camera, but X-ray light sets off the chemical reaction instead of visible light. (See How Photographic Film Works to learn about this process.)

Generally, doctors keep the film image as a negative. That is, the areas that are exposed to more light appear darker and the areas that are exposed to less light appear lighter. Hard material, such as bone, appears white, and softer material appears black or gray. Doctors can bring different materials into focus by varying the intensity of the X-ray beam.

Answer 3

X-Rays are the product of electron interactions. In a x-ray tube, electrons are accelerated to very high speeds. They hit a metal target that has a high atomic number (such as tungsten). The interaction of the electron with the target produces either Bremstralung radiation or Characteristic X-rays (in addition to heat production).

Bremstralung radiation occurs when an electron is attracted to the positively charged nucleus. The electron passes by the nucleus, slows down, and in the process, loses some energy by emitting photons of light or x-rays.

Characteristic x-rays are produced when an energetic electron directly hits another electron in the inner shell of a target atom. The target electron is knocked out, thereby leaving a vacant spot for the outer shell electrons to fall into the lower energy inner shell. This process releases electromagnetic energy in the form of photons or x-rays.


for more detail .............

[e-mail]

Answer 4

The Photoelectric effect.

Answer 5

photoelectric effect