Explain why hot air is lighter than cold air.

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The density of air is related to the refractive index of the medium. The refractive index is the ratio of the speed of light in a vacuum to the speed of light in a given medium. It is well-known that the speed of light in air increases with temperature, i.e., the refractive index of air decreases with increasing temperature.

When air is heated, it expands and becomes less dense than the surrounding cool air.
The molecules of hot air move faster and farther apart, which reduces the density of the hot air.
The hot air, being less dense, rises above the cooler air, which creates convection currents.
These convection currents are responsible for the movement of heat from the earth's surface to the upper atmosphere, where it can be radiated away into space.
The refractive index of the hot air is lower than that of the cold air, so the hot air rises above the cold air, which is why hot air balloons rise.

In summary, hot air is lighter than cold air due to its lower density, which is caused by the faster movement and further apart of the molecules of hot air. This leads to a lower refractive index of hot air than that of cold air, which causes the hot air to rise above the cold air.

Hot air is lighter than cold air

Hot Air is Lighter than Cold Air

Also check:

Refractive Index – Related Concepts
Total Internal Reflection	Refraction through a Prism	Critical Angle Formula
Kaleidoscope	Some Natural Phenomena due to Sunlight	Wave-Particle Duality
Dispersion by a Prism	Relation Between Critical Angle and Refractive Index	Uses of Convex Mirror
Optical Instruments	Ray Optics and Optical Instruments	Reflection of Light by Spherical Mirrors

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Explain why hot air is lighter than cold air.

CBSE CLASS XII Related Questions

1.
Draw the plot of potential energy of a pair of nucleons as a function of their separation. Write two important conclusions that can be drawn from this plot.

2.
In a region, the electric potential varies as \(V = 10 - 50x\), where \(V\) is in volts and \(x\) is in meters. The electric field in the region is

3.
A rectangular loop of size 5 cm $\times$ 8 cm is lying in the $x$-$y$ plane in a uniform magnetic field $\vec{B} = (2.0\ \text{T})\hat{k}$. The total magnetic flux linked with the loop is:

5.
A magnet held vertically, with its north pole down, is dropped along the axis of a closed solenoid placed vertically on a table. If the observer looks down from the top,

6.
Find the ratio $\dfrac{\lambda_\alpha}{\lambda_p}$ of the de Broglie wavelength $\lambda_\alpha$ associated with an alpha particle to the de Broglie wavelength $\lambda_p$ associated with a proton if both are moving with the same velocity.

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Explain why hot air is lighter than cold air.

CBSE CLASS XII Related Questions

1.Draw the plot of potential energy of a pair of nucleons as a function of their separation. Write two important conclusions that can be drawn from this plot.

2.In a region, the electric potential varies as \(V = 10 - 50x\), where \(V\) is in volts and \(x\) is in meters. The electric field in the region is

3.A rectangular loop of size 5 cm $\times$ 8 cm is lying in the $x$-$y$ plane in a uniform magnetic field $\vec{B} = (2.0\ \text{T})\hat{k}$. The total magnetic flux linked with the loop is:

5.A magnet held vertically, with its north pole down, is dropped along the axis of a closed solenoid placed vertically on a table. If the observer looks down from the top,

6.Find the ratio $\dfrac{\lambda_\alpha}{\lambda_p}$ of the de Broglie wavelength $\lambda_\alpha$ associated with an alpha particle to the de Broglie wavelength $\lambda_p$ associated with a proton if both are moving with the same velocity.

Comments

SUBSCRIBE TO OUR NEWS LETTER

1.
Draw the plot of potential energy of a pair of nucleons as a function of their separation. Write two important conclusions that can be drawn from this plot.

2.
In a region, the electric potential varies as \(V = 10 - 50x\), where \(V\) is in volts and \(x\) is in meters. The electric field in the region is

3.
A rectangular loop of size 5 cm $\times$ 8 cm is lying in the $x$-$y$ plane in a uniform magnetic field $\vec{B} = (2.0\ \text{T})\hat{k}$. The total magnetic flux linked with the loop is:

5.
A magnet held vertically, with its north pole down, is dropped along the axis of a closed solenoid placed vertically on a table. If the observer looks down from the top,

6.
Find the ratio $\dfrac{\lambda_\alpha}{\lambda_p}$ of the de Broglie wavelength $\lambda_\alpha$ associated with an alpha particle to the de Broglie wavelength $\lambda_p$ associated with a proton if both are moving with the same velocity.