Story of X-Rays.

 X-rays, like the light are electromagnetic radiations and are not visible to the eye. Their wavelengths are smaller than those of the visible light. They are high energy rays. That is why they have high penetrating power. They can pass through the flesh of our body. They travel with the velocity of light. 

X-Rays image of the human hand.

These rays were discovered by Prof. Wilhelm Conrad Roentgen in 1895. They are sometimes called 'Roentgen rays' also. They were called X-rays (X-means unknown) because these were not known earlier. For this wonderful discovery Prof. Roentgen was awarded the first Nobel Prize of Physics in 1901 .

Wavelength of the Electro-magnetic waves.

The apparatus used for producing X-rays is called 'X-rays tube'. This tube is made up of hard glass and is fitted with two electrodes which are connected to high voltage D.C. source. The electrode connected to the negative terminal is called cathode and the one connected to positive terminal is called anode. Low pressure is created inside the tube by pumping out air from it. When high voltage is applied between the electrodes, electrons emerge from the cathode and hit the 'anode' or the 'target'. As a result the X-rays come out of the tube. 

X-rays are very useful for us. They can pass through substances like wood, paper, skin, flesh etc. but are absorbed by bones, iron,lead etc. Doctors make use of X-rays to detect the dislocations and fractures of bones. They are also used to examine the diseases of lungs and presence of stones in kidneys and gall bladder. X-rays are allowed to fall on the body part to be examined and a photograph is taken on the photo film kept behind that part. In this film the portion of bones appears grey. From these X-ray photographs, the disease and defects are located easily. 

X-rays are also used in treating cancer. With the help of these rays, gold and other valuable gems hidden in the body are detected easily. They are also used to detect cracks and bubbles in the iron bars used for constructing bridges and buildings. They are used to study the structure of crystals. With these rays, it is very easy to distinguish between natural and synthetic diamonds.  

What are Infra-red Radiations?

We all know that the sunlight consists of all those colours which are seen in a rainbow. These colours are: violet, indigo, blue, green, yellow, orange and red. Light from the sun travels in the form of waves which are known as electromagnetic waves. The different colours of light have different wavelengths. Our eyes are sensitive only to the wavelengths relating to the above seven colours. Apart from the wavelengths of these seven colours, the sunlight consists of radiations of other wavelengths also, but our eyes are not sensitive to them. Rays having wavelengths higher than that of red light are called infra-red rays and those lower than violet light are called ultraviolet rays. Both infra-red and ultraviolet rays are not visible to our eyes.

Spectral Lines.

Infra-red rays come not only from the sun but from every hot object. Burning wood and coal, electric heater-all produce these rays. These can be recorded on special type of photographic films made of infra-red sensitive materials. Whenever these rays fall on any material body they produce heat. They are very useful to us. 

Wavelength 

Wavelength of Infrared Radiation.

Infra-red radiations are being used for the treatment of several diseases. Special types of infra-red lamps are used for treating the pains of muscles and joints-especially for backpain. They are also used for heating rooms in winter.

Animals Pictures taken under IR Camera.

Infra-red radiations are being used for the guidance and control of missiles and other ballistic weapons. These radiations are also used for transmitting and receiving invisible signals. Molecular structures are studied with the help of these radiations. Impurities present in the materials can also be detected by these rays. 

Light, The Visible Reminder of Invisible Light ---John Green---