Physics
(a) State two common properties of γ-rays and X-rays.
(b) Name two main sources of nuclear radiations. How are the nuclear radiations harmful?
Answer
(a) Both γ-rays and X-rays are
- electromagnetic rays.
- undeflected by electric and magnetic fields.
(b) Two main sources of nuclear radiations are:
- Radioactive fall out from nuclear plants — The nuclear power plants are now a major source of electricity in the world. If somehow, there is an accident in the reactor of power plant, a large amount of radioactive material and radiations will escape out into the atmosphere. This will not only affect the population around the plant, but will also affect the life at far off places where they will reach due to air currents.
- Nuclear waste — The nuclear waste are still very radioactive and are a source of harmful radiations therefore, they should not be dumped in the open garbage. They can contaminate water and soil and affect the human and living organisms.
The harmful biological effects of nuclear radiations are of three types:
- Short term recoverable effects like diarrhea, sore throat, loss of hair, nausea, etc.
- Long term irrecoverable effects like leukemia and cancer.
- Genetic effects that appear in the later generations of the person exposed to the radiation as the genes in the living cell get modified.
Related Questions
(a) Name the phenomenon involved in tuning a radio set to a particular station
(b) Define the phenomenon named by you in part (a) above.
(c) What do you understand by loudness of sound?
(d) In which unit is the loudness of sound measured?
Hema uses two appliances in her home. One appliance is rated at 100 W and operates at 220 V, while the other appliance is rated at 60 W and also operates at 220 V. These appliances are connected to the electrical main supply in both series and parallel configurations, as shown in the figure 1 and 2.

(a) Calculate the total power consumption when the two appliances are connected in series.
(b) Calculate the total power consumption when the two appliances are corrected in parallel.
(c) Which configuration results in higher total power consumption, series or parallel?
Five resistors of different resistances are connected together as shown in the figure.
A 12 V battery is connected to the arrangement.

Calculate
(a) total resistance in the circuit.
(b) the total current flowing in the circuit.
An electric heater of power 780 W raises the temperature of 5.5 kg of a lab-chemical from 30°C to 41°C in 1.5 min.
Calculate
(a) energy supplied by heater,
(b) heat capacity and
(c) the specific heat capacity of the lab-chemical.