Infrared Radiation and Light
when a radiant heater or grill is switched on you can detect the infrared radiations coming from it by the heating effects it produces in your skin. in fact all objects emit some infrared because of the motion of their atoms or molecules. most radiate a wide range of wavelengths.
As an object heats up, it radiates more and more infrared and shorter wavelengths. about 700 degree celsius the shortest wavelength radiated can be detected by the eye so the objects glows 'red hot'. above about 1000c the whole of the visible spectrum is covered so the object is 'hot white'.
Short wavelengths infrared is often called 'infrared light' even though it is invisible. however strictly speaking light is just the part of the elctromagnetic spectrum that is visible to the eye.Security alarms and lamps can be switched on by motion sensors that pick up the changing pattern of infarred caused by an approching person.At night,photograps can be taken using infarred.In telephone networks, signals are sent along optical fibers as puless of infarred 'light'.And remote controllers TVs video recoders work by trasmitting infarred puleses.
Ultraviolet Radiation
Very hot objects, such as the Sun, emit some of their radiation beyond the violet end of the visible spectrum. this is ultraviolet radiation. It is sometimes called 'Ultraviolet Light', even thou it is invisible.
The Sun's Ultraviolet is harmful to living cells. If too much penetrates the skin, it will cause skin cancer. If you have black dark skin, the ultraviolet is absorbed before it can penetrate too far. But with fair skin, the ultraviolet can go deeper. The skin develops a tan to try to protect itself against ultraviolet. Ultraviolet can also damage the retina in the eye and cause blindness.
As ultraviolet is harmful to living cells it is used in some type of sterilizing equipment to kill bacteria (germs)
Fluorescence, Some materials fluoresce when they absorb ultraviolet: they convert energy into visible light and glow. In fluorescent lamps, the inside of the tube is coated with a white powder which gives off light when it absorbs ultraviolet. The ultraviolet is produced by passing an electric current through the gas (mercury vapor) in the tube.
X-Ray
X-rays are given off when fast moving electrons lose energy very quickly. For example, in an x-ray tube, the radiation is emitted when a beam of electrons hit the metal target. Short wavelength x-rays are extremely penetrating. A dense metal like lead can reduce their strength, but not stop them. Long wavelength x-rays are less penetrating. For example, they can pass through flesh but not bone, so bones will show up on an X-ray photograph.In engineering , X-rays can be used to take photographs
that can reveal flaws inside metals-for example faulty welds in pipe joints. Airport security systems also use them to detect any weapons hidden in luggage.
All x-rays are dangerous because they damage living cells deep in the body and can cause cancer or mutations (genetic changes). However, concentrated beams of X-rays can be used to treat cancer by destroying abnormal cells.
Gamma Ray
Gamma rays come from radioactive materials.They are produced when the nuclei of unstable atoms break up or lose energy.They tend to have shorter wavelengths than X-rays because the energy changes that produce them are greater:However :there is no difference between X-rays and gamma rays of the same wavelength.
Like X-rays, gamma rays can be used in the treatment of cancer;and for taking X-rays-type photographs.As thet kill harmful bacteria ,they are also used for sterilizing food and medical equipment
when a radiant heater or grill is switched on you can detect the infrared radiations coming from it by the heating effects it produces in your skin. in fact all objects emit some infrared because of the motion of their atoms or molecules. most radiate a wide range of wavelengths.
As an object heats up, it radiates more and more infrared and shorter wavelengths. about 700 degree celsius the shortest wavelength radiated can be detected by the eye so the objects glows 'red hot'. above about 1000c the whole of the visible spectrum is covered so the object is 'hot white'.
Short wavelengths infrared is often called 'infrared light' even though it is invisible. however strictly speaking light is just the part of the elctromagnetic spectrum that is visible to the eye.Security alarms and lamps can be switched on by motion sensors that pick up the changing pattern of infarred caused by an approching person.At night,photograps can be taken using infarred.In telephone networks, signals are sent along optical fibers as puless of infarred 'light'.And remote controllers TVs video recoders work by trasmitting infarred puleses.
Ultraviolet Radiation
Very hot objects, such as the Sun, emit some of their radiation beyond the violet end of the visible spectrum. this is ultraviolet radiation. It is sometimes called 'Ultraviolet Light', even thou it is invisible.
The Sun's Ultraviolet is harmful to living cells. If too much penetrates the skin, it will cause skin cancer. If you have black dark skin, the ultraviolet is absorbed before it can penetrate too far. But with fair skin, the ultraviolet can go deeper. The skin develops a tan to try to protect itself against ultraviolet. Ultraviolet can also damage the retina in the eye and cause blindness.
As ultraviolet is harmful to living cells it is used in some type of sterilizing equipment to kill bacteria (germs)
Fluorescence, Some materials fluoresce when they absorb ultraviolet: they convert energy into visible light and glow. In fluorescent lamps, the inside of the tube is coated with a white powder which gives off light when it absorbs ultraviolet. The ultraviolet is produced by passing an electric current through the gas (mercury vapor) in the tube.
X-Ray
X-rays are given off when fast moving electrons lose energy very quickly. For example, in an x-ray tube, the radiation is emitted when a beam of electrons hit the metal target. Short wavelength x-rays are extremely penetrating. A dense metal like lead can reduce their strength, but not stop them. Long wavelength x-rays are less penetrating. For example, they can pass through flesh but not bone, so bones will show up on an X-ray photograph.In engineering , X-rays can be used to take photographs
that can reveal flaws inside metals-for example faulty welds in pipe joints. Airport security systems also use them to detect any weapons hidden in luggage.
All x-rays are dangerous because they damage living cells deep in the body and can cause cancer or mutations (genetic changes). However, concentrated beams of X-rays can be used to treat cancer by destroying abnormal cells.
Gamma Ray
Gamma rays come from radioactive materials.They are produced when the nuclei of unstable atoms break up or lose energy.They tend to have shorter wavelengths than X-rays because the energy changes that produce them are greater:However :there is no difference between X-rays and gamma rays of the same wavelength.
Like X-rays, gamma rays can be used in the treatment of cancer;and for taking X-rays-type photographs.As thet kill harmful bacteria ,they are also used for sterilizing food and medical equipment
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