Physics - General Knowledge Questions and Answers

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Which of the following colours is not a primary colour?

A)
White

B)
Green

C)
Red

D)
Blue


Correct Answer :

White


Explanation :

The Primary Colors, Yellow, Red and Blue, are at the top of any color, And can be any colors used to make other colors

The Secondary colors are Orange, Purple and Green , And are combinations of two primary colors.
red + blue = purple
red + yellow = orange
yellow + blue = green

The Tertiary colors are the six 'in-between' colors. They are each a mixture of one Primary Color plus its nearest Secondary.
yellow + orange = yellow-orange
red + orange = red-orange
red + purple (violet) = red-purple (red-violet)
blue + purple (violet) = blue-purple (blue-violet)
blue + green = blue-green
yellow + green = yellow-green

To correct the defect Myopia or near sightedness, we have to use?

A)
convex lens

B)
concave lens

C)
plane glass

D)
None of these


Correct Answer :

concave lens


Explanation :

Myopia is the term used to define short sightedness.A myopic person has clear vision when looking at objects close to them, but distant objects will appear blurred.
A concave lens is placed in front of a myopic eye, moving the image back to the retina and clarifying the image.

Whereas Hypermetropia means long sight .a hypermetropic person may have blurred vision when looking at objects close to them, and clearer vision when looking at objects in the distance.
A convex lens in front of a hypermetropic eye, the image is moved forward and focuses correctly on the retina.

The pitch of a sound depends upon its?

A)
Amplitude

B)
Frequency

C)
Quality

D)
None of these


Correct Answer :

Frequency


Explanation :

The pitch of sound is directly related to frequency. Higher frequency refers to a higher pitched wave and a low frequency produces a low pitched note.

Whereas frequency is measured in Hertz (Hz), with one vibration per second being equal to one hertz (1 Hz).

Protections from ultraviolet rays coming from sun is provided by?

A)
SO2

B)
CO2

C)
Ozone

D)
Oxygen


Correct Answer :

Ozone


Explanation :

Ultraviolet (UV) radiation is a major risk factor for most skin cancers. Sunlight is the main source of UV rays.

Ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet (UV) radiation.Ozone molecule contains three oxygen atoms (O3).

Ozone is found in two different layers of the atmosphere - the troposphere and the stratosphere. The stratospheric ozone, or "good ozone," protects life on earth from harmful effects of the sun's UV rays. Tropospheric ozone, or "bad ozone," is an air pollutant that damages human health, vegetation, and many common materials.

Polar satellites completed its orbit in about?

A)
2 hours

B)
8 hours

C)
16 hours

D)
24 hours


Correct Answer :

2 hours

Milky way is a?

A)
Elliptical galaxy

B)
Oval galaxy

C)
Spiral galaxy

D)
Round galaxy


Correct Answer :

Spiral galaxy


Explanation :

Our Sun (a star) and all the planets around it are part of a galaxy known as the Milky Way Galaxy.
The Milky Way is a barred spiral galaxy with a diameter between 100,000 and 180,000 light-years. The Milky Way is estimated to contain 100–400 billion stars.

The value of escape velocity on the earth is ?

A)
11.16 km/h

B)
11.16 km/min

C)
11.6 m/s

D)
11.16 km/s


Correct Answer :

11.16 km/s


Explanation :

Escape velocity is the speed that an object needs to be traveling to break free of a planet or moon's gravity well and leave it without further propulsion. For example, a spacecraft leaving the surface of Earth needs to be going 7 miles per second, or nearly 25,000 miles per hour to leave without falling back to the surface or falling into orbit.

On the surface of the Earth, the escape velocity is about 11.2 km/s.

Speed of light in different mediums is different. This cause -

A)
Reflection

B)
Refraction

C)
Dispersion

D)
Rarefaction


Correct Answer :

Refraction


Explanation :

REFRACTION: the phenomenon of deviation of light rays from their original path while passing from one medium to another due to change of speed of light in other medium is called refraction.

REFLECTION: When light falling on a surface retraces back into the same medium , it is said to be reflected.

The magnetic effect of current was discovered by?

A)
Fleming

B)
Maxwell

C)
Oersted

D)
Faraday


Correct Answer :

Oersted


Explanation :

Oersted's law, is the physical law stating that an electric current creates a magnetic field.

This was discovered on 21 April 1820 by Danish physicist Hans Christian Ørsted (1777–1851),when he noticed that the needle of a compass next to a wire carrying current turned.

Which metal is best to make the filament of the bulb?

A)
Gold

B)
Tungsten

C)
Aluminium

D)
Copper


Correct Answer :

Tungsten


Explanation :

Tungsten, also known as wolfram, is a chemical element with symbol W and atomic number 74.
Tungsten has the highest melting point of all metallic elements and is used to make filaments for incandescent light bulbs, fluorescent light bulbs and television tubes.

A solar cell is made up of?

A)
Silicon

B)
Titanium

C)
Magnesium

D)
Teflon


Correct Answer :

Silicon


Explanation :

Silicon is a semiconductor material. When it is doped with the impurities gallium and arsenic its ability to capture the sun's energy and convert it into electricity is improved considerably.

An image formed by a plane mirror could not be obtained on a screen. Such an image is called a/an________.

A)
Real image

B)
Inverted image

C)
Virtual image

D)
Perfect image


Correct Answer :

Virtual image


Explanation :

Any image that can be formed on a screen are called real image. Such images are formed by light rays emanating from the object.

Images formed by plane mirrors are virtual (meaning that the light rays do not actually come from the image).

Mirrors are used by dentists to see an enlarged image of teeth. These mirrors are?

A)
Concave

B)
Convex

C)
Plane

D)
Spherical


Correct Answer :

Concave


Explanation :

Dentist use concave mirror so that he/she will be able to see the magnified view of patients affected teeth.

The number of images of an object placed between two mirrors inclined at an angle of 45o are:?

A)
5

B)
6

C)
7

D)
8


Correct Answer :

7


Explanation :

If two plane mirrors are inclined at angle x, then the number of images formed in them is given by the formula:

Number of images formed = ( 360° /x ) - 1

By substituting the different values of angles between two inclined mirrors we can tabulate the number of images formed as follows:

Angle between the two mirrors Number of images formed
45° 7
60° 5
90° 3
120° 2
180° 1
Infinite

A steel wire has a magnetic movement M. If the wire is bend into semicircular arc, The new magnetic movement becomes?

A)
M

B)
2M

C)
2πM

D)
(2/π)*M


Correct Answer :

(2/π)*M


Explanation :


Let 2L = length of the bar magnet , then
magnetic moment,M = m * 2L

After bent into semicircle
πR = 2L (as circumference of a semi-circle = πR + 2*R )
R = 2L / π

When the magnet is bent in the form of a semicircle, the distance between the poles = 2R = 2 * (2L / π)

New magnetic moment = m * 2 * (2L / π) = 2M / π

The surface of a spherical shell is uniformly charged. Then what is the electric field inside the spherical shell?

A)
Zero

B)
constant

C)
Infinite

D)
Proportional to the distance from the center


Correct Answer :

Zero


Explanation :

According to Gauss law all charges are distributed on the surface of the spherical shell. Therefore there will be no electric flux inside the spherical shell,So that the electric field inside the shell will be zero.

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