Tag: physics

Questions Related to physics

State whether true or false :
Solar dryer can be used in night also.

  1. True

  2. False


Correct Option: B
Explanation:

At night there is no sunlight to produce heat energy so we cannot use solar cookers in night.

State whether true or false :
The purpose of glass cover placed on solar dryer is to sustain the heat.

  1. True

  2. False


Correct Option: A

The purpose of black coloured box in a solar dryer is to :

  1. Absorb more heat

  2. Absorb less heat

  3. Reflect light

  4. None of these


Correct Option: A
Explanation:

We use the black coloured box to absorb more heat as black colour is the best absorber for heat among its all colours.

Find the distance between the pairs of points whose cartesian coordinates are $(2,3,-1), (2,6,2).$

  1. $\displaystyle 3\sqrt{2}.$

  2. $\displaystyle 2\sqrt{3}.$

  3. $\displaystyle 5\sqrt{2}.$

  4. $\displaystyle 2\sqrt{5}.$


Correct Option: A
Explanation:

Distance Between two points $(a,b,c)$ and $(x,y,z)$ is given by
$\sqrt { \left( a-x \right) ^{ 2 }+\left( b-y \right) ^{ 2 }+\left( c-z \right) ^{ 2 } } $
Given $(2,3,-1)$, $(2,6,2)$
Distance $=\sqrt { \left( 2-2 \right) ^{ 2 }+\left( 3-6 \right) ^{ 2 }+\left( -1-2 \right) ^{ 2 } } $
                $=\sqrt { 18 } $
                $=3\sqrt { 2 }$

Find the distance between the points whose position vectors are given as follows

$(-1,1,3), (0,5,6)$

  1. $\displaystyle \sqrt{118}$

  2. $8$

  3. $\displaystyle \sqrt{26}$

  4. none of these


Correct Option: C
Explanation:

Distance Between two points $(a,b,c)$ and $(x,y,z)$ is given by
$\sqrt { \left( a-x \right) ^{ 2 }+\left( b-y \right) ^{ 2 }+\left( c-z \right) ^{ 2 } } $
Given $(-1,1,3)$, $(0,5,6)$
Distance $=\sqrt { \left( -1-0 \right) ^{ 2 }+\left( 1-6 \right) ^{ 2 }+\left( 3-6 \right) ^{ 2 } } $
                $=\sqrt { 26 } $

Find the distance between the points whose position vectors are given as follows

$-2\hat i+3\hat j+5\hat k, 7\hat i-\hat k$

  1. $\displaystyle 3\sqrt{14}$

  2. $\displaystyle \sqrt{54}$

  3. $\displaystyle 3\sqrt{19}$

  4. $\displaystyle \sqrt{57}$


Correct Option: A
Explanation:

Distance Between two position vectors $a\hat i+b\hat j+c\hat k$ and $x\hat i+y\hat j+z\hat k$ is given by
$\sqrt { \left( a-x \right) ^{ 2 }+\left( b-y \right) ^{ 2 }+\left( c-z \right) ^{ 2 } } $
Given $-2\hat i+3\hat j+5\hat k$, $7\hat i-\hat k$
Distance $=\sqrt { \left( -2-7 \right) ^{ 2 }+\left( 3-0 \right) ^{ 2 }+\left( 5+1 \right) ^{ 2 } } $
                $=\sqrt { 126 } $
                $=3\sqrt { 14 } $

Find the distance between the points whose position vectors are given as follows

$4\hat i+3\hat j-6\hat k, -2\hat i+\hat j-\hat k$

  1. $\displaystyle \sqrt{65}$

  2. $\displaystyle \sqrt{69}$

  3. $13$

  4. none of these


Correct Option: A
Explanation:

Distance Between two position vectors $a\hat i+b\hat j+c\hat k$ and $x\hat i+y\hat j+z\hat k$ is given by
$\sqrt { \left( a-x \right) ^{ 2 }+\left( b-y \right) ^{ 2 }+\left( c-z \right) ^{ 2 } } $
Given $4\hat i+3\hat j-6\hat k$, $-2\hat i+\hat j-\hat k$
Distance $=\sqrt { \left( 4+2 \right) ^{ 2 }+\left( 3-1 \right) ^{ 2 }+\left( -6+1 \right) ^{ 2 } } $
                $=\sqrt { 65 } $

We consider the radiation emitted by the human body. Which of the following statements is true :

  1. The radiation emitted is in the infrared region

  2. The radiation is emitted only during the day

  3. The radiation is emitted during the summers and absorbed during the winters

  4. The radiation emitted lies in the ultraviolet region and hence is not visible


Correct Option: A
Explanation:

Every body at all time, at all temperatures emit radiation (except at T = 0), which fall in the infrared region.

The decreasing order of wavelength of infrared, microwave, ultraviolet and gamma rays is

  1. Microwaves, Infrared, ultraviolet, gamma rays.

  2. Infrared, Microwaves, ultraviolet, gamma rays.

  3. ultraviolet, gamma rays, Infrared, Microwaves

  4. Microwaves, gamma rays, Infrared, ultraviolet


Correct Option: A
Explanation:

The wavelength of the Electromagnetic waves is inversely proportional to the frequency of the wave. The frequency of the gamma rays is highest whereas the ultraviolet, Infrared and microwaves follow in decreasing order.
Therefore, the decreasing order of wavelengths will be opposite to the frequency order. So, the microwaves have the longest wavelength and the gamma rays have the smallest.

Microwave $>$ Infrared $>$ Ultraviolet $>$Gamma ray.

The part of the spectrum of electromagnetic radiation used to cook food is

  1. Ultraviolet rays

  2. Cosmic rays

  3. X rays

  4. Microwaves


Correct Option: D
Explanation:

Microwaves are used to cook food. Microwave oven is a domestic application of these waves.