Alpha ray
- (a) It is a stream of alpha particles, each particle containing two protons and two neutrons. An alpha particle is nothing but a helium nucleus.
- (b) Being made of positively charged particles, alpha ray can be deflected by an electric field as well as by a magnetic field.
- (c) Its penetrating power is low. Even in air, its intensity falls down to very small values within a few centimetres.
- (d) Alpha rays coming from radioactive materials travel at large speeds of the order of 10 6 m s-1.
- (e) All the alpha particles coming from a particular decay scheme have the same energy.
- (f) Alpha ray produces scintillation (flashes of light) when it strikes certain fluorescent materials, such as barium platinocyanide.
- (g) It causes ionization in gases.
Beta ray
- (a) It is a stream of electrons coming from the nuclei. Thus, the properties of beta ray, cathode ray, thermions, photoelectrons, etc., are all identical except for their origin. Beta particles are created at the time of nuclear transformation, whereas, in cathode ray, thermions, etc., the electrons are already present and get ejected.
- (b) Being made of negatively charged particles, beta ray can be deflected by an electric field as well as by a magnetic field.
- (c) Its penetrating power is greater than that of alpha ray. Typically, it can travel several metres in air before its intensity drops to small values.
- (d) The ionizing power is less than that of alpha rays.
- (e) Beta ray also produces scintillation in fluorescent materials, but the scintillation is weak. (f) The energy of the beta particles coming from the same decay scheme are not equal. This is because the available energy is shared by antineutrinos. The energy of beta particles thus varies between zero and a maximum.
Beta-plus ray
- Beta-plus ray has all the properties of beta ray, except that it is made of positively charged particles.
Gamma ray
- (a) Gamma ray is an electromagnetic radiation of short wavelength. Its wavelength is, in general, smaller than X-rays. Many of its properties are the same as those of X-rays.
- (b) Being chargeless, it is not deflected by electric or magnetic field.
- (c) It has the least ionizing power and the largest penetrating power among different types of nuclear radiation.
- (d) All the photons coming from a particular gamma decay scheme have the same energy.
- (e) Being an electromagnetic wave, gamma ray travels in vacuum with the velocity c.
Nuclear radiation, specially gamma ray, is used in medicine for cancer therapy and other treatments. The ionizing power of nuclear radiation is used in factories to avoid accumulation of charge on moving parts due to friction. Presence of radioactive material ionizes the air and any charge accumulated leaks away. Carbon dating, which is based on radioactive decay of 14C, is a reliable technique to estimate the ‘age’ of archeological samples which have carbon contents. Excess exposure to nuclear radiation is harmful for human body.
