Option “1” is correct. C.F.L. is short for Compact Fluorescent Lamp. CFL uses significantly less energy than traditional light bulbs (75% less).
323. Sky is blue because-
1. Blue colour in the sunlight is more than other colours
2. Short waves are scattered more than long waves by atmosphere
3. Blue colour is more absorbing to eyes
4. Atmosphere absorbs long wavelength more than short wavelength
Option “2” is correct. Blue light which has the least wavelength of all the visible radiations is scattered most. The blue appearance of the sky is due to scattering of sunlight from the atmosphere. Light of shorter wavelength is scattered by air molecules which because of their smaller size follow Rayleigh’s scattering. Blue light is strongly scattered by the air molecules and reach the observer. This explains the blue colour of the sky.
324. As per the WHO, the safe noise level for a city is-
1. 45 db
2. 50 db
3. 55 db
4. 60 db
Option “1” is correct. As per the WHO the safe noise level for a city is 45 decibel (db).
325. Which one of the following does a TV remote control unit use to operate a TV set?
Option “4” is correct. Infrared waves are used to transmit radio and TV signals but some of them are using radio waves. Infrared is an electromagnetic radiation.
326. Which instrument is used to measure sound under water?
Option “4” is correct. A hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound.
327. While floating in a sea what part of an iceberg is below the surface of the sea?
1. 1/9
2. 1/3
3. 1/6
4. 1/4
Option “1” is correct. When pure water changes into the ice at 4°C, the density of ice so formed is 1/9th of the density of water. Therefore, in pure water, 90% part of the ice must be below the surface of the water and remaining 10% part must be above the surface. Sea water has high density (salty) water but the ice formed by it is pure and not salty. Therefore option (a) is correct.
328. What type of energy in wind blowing?
1. Only potential
2. Only kinetic
3. Electrical
4. Potential and kinetic both
Option “2” is correct. The kinetic energy in the energy in moving objects or mass. The kinetic energy of the wind (wind energy) can be converted into electrical or mechanical energy.
329. Which one among the following has the highest energy?
1. Blue light
2. Green light
3. Red light
4. Yellow light
Option “1” is correct. Energy ∝1/(wave length) The energy of any of the colour is inversely proportional to its wavelength. According the VIBGYOR violet, Indigo and blue have the minimum wavelength, thus they have maximum energy level. So according to the options given in the question, blue has the maximum energy while red had the minimum energy.
330. The apparatus used to measure the intensity of light is known is-
1. Anemometer
2. Thermometer
3. Lux meter
4. Altimeter
Option “3” is correct. Luxmeter is used to measure the intensity of light, while colorimeter is a device used to measure the intensity of colour.
