8
Q:

Two metallic plate of equal thickness and coefficient thermal conductivity K1 and K2 put together face to face. A common plate is constructed. What is equivalent K?

 A) K1k2/k1+k2 B) 2k1k2/k1+k2 C) K1+k2/k1k2 D) None

Explanation:

We know that,

The equivalent K =

where L1 & L2 are plate1 & Plate2 thicknesses, K1 & K2 are coefficient thermal conductivity of plate1 & Plate2 respectively.

But here L1 = L2 = L (say)

Then K = L+L/(L/K1 + L/K2)  =  $\frac{\mathbf{2}\mathbf{K}\mathbf{1}\mathbf{K}\mathbf{2}}{\mathbf{K}\mathbf{1}\mathbf{+}\mathbf{K}\mathbf{2}}$

Subject: Physics
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Q:

Which Color has the Longest Wavelength?

 A) Violet B) Yellow C) Red D) White

Explanation:

The visible colors from Longest wavelength to Shortest wavelength are :: Red, Orange, Yellow, Green, Blue and Violet.

Red > Orange > Yellow > Green > Blue > Violet.

1. Infrared radiation has a longer wavelength than visible Red light.

2. Ultraviolet radiation has a shorter wavelength than the visible violet light.

3. The white light is a mixture of the colors of the visible spectrum.

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3 89
Q:

Which of the following is Not a form of Energy?

 A) Heat B) Sound C) Motion D) Pressure

Explanation:

Pressure is Not a form of Energy.

Energy : It is defined as the ability to do work.

Energy comes in two basic forms. They are :

1. Potential Energy

2. Kinetic Energy

Potential Energy is any type of stored energy. It can be chemical, nuclear, gravitational, or mechanical.

Kinetic Energy is found in movement. An airplane flying or a meteor plummeting each have kinetic energy. Even the tiniest things have kinetic energy, like atoms vibrating when they are hot or when they transmit sound waves. Electricity is the kinetic energy of flowing electrons between atoms.

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3 71
Q:

How long would it take to travel 4 light years?

There are approximately 6 trillion miles in a light-year, so the distance we need to go is 6 trillion miles / light-year times. 4 light-years is equal to 24 trillion miles. So, this whole would take 1.2 billion hours. There are 24 hours a day and 365.25 days per year, so this time in years is 137 thousand years.

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73
Q:

The Length of the Day is determined in

 A) length of the hours B) length of the year C) astronomical units D) solar terms

Explanation:

The Length of the Day is determined in Astronomical Units.

The length of a day corresponds to the time the Earth takes to turn around on its axis, which is approximately 24 hours. But it's not exactly 24 hours.

This phenomenon is due to tides raised by the Moon which slow Earth's rotation. Because of the way the second is defined, the mean length of a day is now about 86 400.002 seconds, and is increasing by about 1.7 milliseconds per century.

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3 74
Q:

The Capacity of a Communication Channel is Measured in

 A) Band rate B) Band width C) Data flow D) Bit capacity

Explanation:

The path that data takes from source to destination is called a Channel. A channel is a communication medium. A channel has a certain capacity for transmitting information.

The "capacity" of a channel is the theoretical upper-limit to the bit rate over a given channel that will result in negligible errors. Channel capacity is often measured by its Bandwidth in Hz or its data rate in bits per second.

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2 67
Q:

Electrical Pressure is also called

 A) Current B) Voltage C) Resistance D) Power

Explanation:

Electrical Pressure is also called as Voltage. Voltage is measured in Volts.

Volt : A unit of electrical pressure or Voltage is called Volt.

One volt is the amount of pressure required to cause one ampere of current to flow against one ohm of resistance.

Voltage is also referred to as Electromotive Force or Electrical Potential or Electrical Pressure.

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6 104
Q:

The wavelength of a wave is the distance between

 A) Crest and Trough B) Crest and Crest C) Trough and Trough D) Both B & C

Explanation:

Distance between two Consecutive Crests or two Consecutive Troughs is called Wavelength. But the distance between crest and adjacent trough is half the wavelength.

That is the distance between adjacent crest and trough is called Half the wavelength.

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8 133
Q:

Mirage is an example of

 A) Reflection of light & Refraction of light B) Dispersion of light C) Total Internal Reflection D) Refraction of light & Total Internal Reflection of light

Answer & Explanation Answer: D) Refraction of light & Total Internal Reflection of light

Explanation:

A Mirage is a naturally occurring optical phenomenon in which light rays bend to produce a displaced image of distant objects or the sky.

• It is caused due to Total internal Reflection.
• It is an optical illusion observed in deserts or hot summer days due to which a person sees a pond of water some distance ahead of him in which the surrounding objects appear inverted.

How Mirage Forms::

1. The temperature of other layers of atmosphere goes on decreasing as we go up.
2. Therefore density and refractive index of air changes as one goes up.
3. Thus a ray of light,gets refracted more and more away from the normal.
4. At a particular angle when a ray of light exceeds critical angle, total internal reflection takes place and ray of light gets reflected in the same medium.
5. when the reflected ray reaches our eye, it appears as coming from tree or sky .
6. Hence the inverted image of tree creates an impression from a pond of water.