1. Lux is the SI unit of
a) intensity of illumination
b) luminous efficiency
c) luminous flux
d) luminous intensity
Explanation: The SI unit of intensity of illumination (illuminance) is the lux. An illuminance of 1.0 lux is produced by 1.0 lumen of light shining on an area of 1.0 m2.
2. On a rainy day, small oil films on water show brilliant colours. This is due to
a) dispersion
b) interference
c) diffraction
d) polarization
Explanation: On a rainy day, small oil films on water show brilliant colours. This is due to Interference.
Interference is a phenomenon in which two waves superimpose to form a resultant wave of greater, lower or same amplitude.
3. Point A is at a lower electrical potential than point B. An electron between them on the line joining them will
a) Move towards A
b) Move towards B
c) Move at right angles to the line joining A and B
d) Remain at rest
Explanation: Since we know that electric currents move from a higher potential or a lower potential. Also, electrons move in the direction opposite to electric current. So the electron on the line joining two points A and B will move from lower to higher potential i.e, it will move towards B.
4. Materials for rain-proof coats and tents owe their water-proof properties to
a) surface tension
b) viscosity
c) specific gravity
d) elasticity
Explanation: The material of rain proof coats have the property of not minimizing the surface tension which will tend the water molecule to be in its drop form.
5.RADAR is used for:
a) locating submerged submarines.
b) receiving a signals in a radio receiver.
c) locating geostationary satellites.
d) detecting and locating the position of objects such as Aeroplanes.
Explanation: RADAR is used for detecting and locating the position of objects such as Aeroplanes.
6. Supersonic plane fly with the speed
a) less than the speed of sound
b) of sound
c) greater than the speed of sound
d) of light
Explanation: Vehicles that fly at supersonic speeds are flying faster than the speed of sound.
7.Mach number is used in connection with the speed of
a) sound
b) aircraft
c) spacecraft
d) ships
Explanation: Mach number is used in connection with the speed of aircraft.
8. On a stationary sail boat, air is blown from a fan attached to the boat. The boat
a) moves in opposite direction in which the air is blown
b) does not move
c) moves in the same direction in which air blows
d) spins around
Explanation: In this case air blown by the fan will try to push the sail boat in a certain direction. But at the same time due to Newton's third law of motion the fan will experience a force due to the air blown in a direction opposite to the direction in which the sail boat will experience the force due to the blown air. So, as a whole the system will be at rest and it will not move.
9. Rainbow is due to
a) absorption of sunlight in minute water droplets
b) diffusion of sunlight through water droplets
c) ionisation of water deposits
d) refraction and reflection of sunlight by water droplets
Explanation: A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured circular arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun.
10. Stars which appear single to the naked eye but are double when seen through a telescope are
a) novas and supernovas
b) binaries
c) asteroids
d) quasars
Explanation: They are single to naked eye because they are far from us. But, if we see with telescope We can observe that there are two or double stars.