## Physics GK Quiz-33

Physics Multiple Choice Questions (MCQs) Quiz for State and UPSC Civil Services Examinations. Objective Questions on Physics for competitive examinations.

### 641. Light year is a unit of

(1) Light

(2) Current

(3) Distance

(4) Time

Answer:

641. (3) A light-year is a unit of length used informally to express astronomical distances. It is equal to just under 10 trillion kilometres.

### 642. The word ‘insolation’ means

(1) matters which insulate

(2) incoming solar radiation

(3) insoluble matters

(4) None of the above

Answer:

642. (2) Insolation is the solar radiation that reaches the earth’s surface. It is measured by the amount of solar energy received per square centimeter per minute. Insolation affects temperature. The more the insolation, the higher is the temperature.

### 643. While ascending a hill, the driver of the vehicle keeps the gear ratio

(1) equal to 1

(2) less than 1

(3) greater than 1

(4) either equal to or greater than 1

Answer:

643. (4) While ascending a hill Gear Ratio should be “Either equal to or greater than 1?. Gear Ratio is the ratio between angular velocity of input gear to the angular velocity of output gear. It prevents the vehicle from stalling.

### 644. A wire of resistance R is cut into ‘n’ equal parts. These parts are then connected in parallel. The equivalent resistance of the combination will be

(1) nR

(2)R/n

(3)n/R

(4)R/2n

Answer:

644. (4) Since R is directly proportional to length of the wire, when wire is cut into equal parts, then Resistance of each part = R/n When the wires are connected in parallel, then the equivalent resistance of combination is 1/R2 = n/R + n/R + n/R ....n times or, 1/R2 = n2R or, R 2 = R/n2

### 645. A moving neutron collides with a stationary a – particle. The fraction of the kinetic energy lost by the neutron is

(1)1/4

(2)1/16

(3)9/25

(4)16/25

Answer:

645. (4)

### 646. Which of these waves can be polarized ?

(1) Sound waves in air

(2) Longitudinal waves on a string

(3) Transverse waves on a string

(4) Light waves

Answer:

646. (4) It is possible to transform unpolarized light into polarized light. A light wave that is vibrating in more than one plane is referred to as unpolarized light. Polarized light waves are light waves in which the vibrations occur in a single plane. The process of transforming unpolarized light into polarized light is known as polarization.

### 647. The unit of Planck’s constant is

(1) Js

(2) Js–2

(3) J/s

(4) Js2

Answer:

647. (1) The Planck constant has dimensions of physical action; these are the same as those of angular momentum, i.e., energy multiplied by time, or momentum multiplied by distance. In SI units, the Planck constant is expressed in joule seconds (J·s) or (N·m·s).

### 648. If a wire of resistance R is melted and recast to half of its length, then the new resistance of the wire will be

(1)R/4

(2)R/2

(3) R

(4) 2R

Answer:

648. (1) The new resistance is one-fourth of the original resistance.

### 649. Golden view of sea shell is due to

(1) Diffraction

(2) Dispersion

(3) Polarization

(4) Reflection

Answer:

649. (3) When a ray of light falls on sea shell, its small amount gets refracted (slightly polarized) and rest almost gets reflected back (fully polarized). So it gets a golden view because of polarization.

### 650. An object covers distance which is directly proportional to the square of the time. Its accelaration is

(1) increasing

(2) decreasing

(3) zero

(4) constant

Answer:

650. (4) When an object covers distance which is directly proportional to the square of the time, its acceleration is constant. This is seen in the cases of falling objects. This connection between time and distance was first observed by Galileo.

### 651. If the horizontal range of a projectile is four times its maximum height, the angle of projection is

(1) 30°

(2) 45°

(3) sin–1 1 4

(4) tan–1 1 4

Answer:

651. (2)

### 652. Rainbow is formed due to

(1) refraction and dispersion

(2) scattering and refraction

(3) diffraction and refraction

(4) refraction and reflection

Answer:

652. (4) A rainbow is an optical phenomenon that is caused by both reflection and refraction of light in water droplets resulting in a spectrum of light appearing in the sky. It is caused by light being refracted (bent) when entering a droplet of water, then reflected inside on the back of the droplet and refracted again when leaving it.

### 653. The boiling point of water decreases at higher altitudes is due to

(1) low temperature

(2) low atmospheric pressure

(3) high temprature

(4) high atmospheric pressure

Answer:

653. (2) At higher altitudes, the air pressure is decreased, which forces water’s boiling point to lower. The air pressure decreases with altitude because of the decrease in the density of air. The lowered boiling point of water requires an increase in cooking times or temperature.

### 654. Which of the following have the same unit ?

(1) Work and power

(2) Torque and moment of inertia

(3) Work and torque

(4) Torque and angular momentum

Answer:

654. (3) The SI unit of work is the Newton-metre or joule (J). A Newton meter is also the SI unit of torque (also called “moment” or “moment of force”).

### 655. In a particular system, the units of length, mass and time are chosen to be 10 cm, 10 g and 0.1 s respectively. The unit of force in this system will be equivalent to

(1) 0.1 N

(2) 1 N

(3) 10 N

(4) 100 N

Answer:

655. (1)

### 656. Distances of stars are measured in

(1) Galactic unit

(2) Stellar mile

(3) Cosmic kilometre

(4) Light year

Answer:

656. (4) Light year is a unit of length used informally to express astronomical distances. It is most often used when expressing distances to stars and other distances on a galactic scale. It is equal to just under 10 trillion kilometres.

### 657. Loudness of sound depends on

(1) Frequency

(2) Wavelength

(3) Amplitude

(4) Pitch

Answer:

657. (3) Loudness depends on the amplitude of the sound wave. The larger the amplitude the more energy the sound wave contains therefore the louder the sound. The pitch of a note depends on the frequency of the source of the sound.

### 658. A man standing at the top of a tower has two spheres A and B. He drops sphere A downwards and throws sphere B horizontally at the same time. Which of the following is correct ?

(1) Both the spheres will reach the ground simultaneously.

(2) A will reach the ground first.

(3) B will reach the ground first.

(4) The question is incomplete because the masses of the spheres are not given.

Answer:

658. (1) If no air resistance is present, the rate of descent depends only on how far the object has fallen, no matter how heavy the object is. This means that two objects will reach the ground at the same time if they are dropped simultaneously from the same height. This statement follows from the law of conservation of energy.

### 659. The dimensional formula ML–1T–2 corresponds to

(1) Modulus of elasticity

(2) Viscosity

(3) Moment of a force

(4) Thrust

Answer:

659. (1) M L-1 T-2 is the dimension of any quantity that is force per unit area such as Pressure or Stress, Young’s Modulus, Bulk Modulus, Modulus of Rigidity, Energy Density. The Modulus of Elasticity is the ratio of the stress applied to a body or substance to the resulting strain within the elastic limit.

### 660. 1 Micron is equal to

(1) 10–9 m

(2) 10–12m

(3) 10–6 m

(4) 10–15 m

Answer:

660. (3) The micrometer or micron, is an SI derived unit of length equaling 1×10–6 of a metre, i.e., one millionth of a metre. It is a common unit of measurement for wavelengths of infrared radiation as well as sizes of cells and bacteria and is commonly used in plastics manufacturing.

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