Physics

Infrared radiation is a part of the electromagnetic spectrum which is specifically used in night detection techniques to enhance visibility. They have a wavelength of around 700 nm to 1 mm and have a frequency range of around 10^12 Hz.

There are different types of electromagnetic waves and each of them have different wavelengths. Human eye can only see the light rays which have a minimum wavelength of around 400-700nm. Rays which don't meet this threshold will eventually not be visible to the humans.

${?}_1=\frac{3}{5}{E}_0\left(0.2\right)N{m}^2{C}^{-1},and{?}_2=\frac{4}{5}{E}_0\left(0.3\right)N{m}^2{C}^{-1}$

$\Rightarrow \frac{{?}_1}{{?}_2}=\frac{3*0.2*5}{5*0.3*4}=\frac{1}{2}$

It depends on the frequency of the wave. Rays such as Gamma rays, X-Rays etc. have higher frequencies which can lead to harmful impacts if exposed to the human body. These kind of rays cannot be even produced easily unlike low frequency rays.

Let v is velocity at the highest position.

$T_{max}=5T_{min}\Rightarrow mg+\frac{m\left(v^2+4g\mathcal{l}\right)}{\mathcal{l}}=5\left(\frac{m{v}^2}{\mathcal{l}}-mg\right)\Rightarrow 4.\frac{v^2}{\mathcal{l}}=10g$

$\Rightarrow v=\sqrt[]{\frac{5}{2}g\mathcal{l}}=\sqrt[]{\frac{5}{2}*10*1}=5m/s$

$\Delta U+\Delta KE=0$

$\Rightarrow \frac{f}{2}nR\Delta T=\frac{1}{2}m{v}^2\Rightarrow \Delta T=\frac{m}{n}\frac{v^2}{fR}=4*10^{-3}*\frac{30^2}{3R}=\frac{3.6}{3R}K.$

The following are the topics covered in this chapter: Electric Field and Field Lines, Gauss's Law, Electric Dipole, Conductors and Insulators, and Electric Flux. 

For equilibrium,

$\frac{dU}{dr}=0\Rightarrow \frac{-10\alpha }{r^{11}}+\frac{5\beta }{r^6}=0\Rightarrow r={\left(\frac{2\alpha }{\beta }\right)}^{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$5$}\right.}$

$L\frac{di}{dt}=V\Rightarrow 2di=3tdt\Rightarrow 2{\displaystyle \underset{0}{\overset{i}{\int }}di=3}{\displaystyle \underset{0}{\overset{4}{\int }}tdt\Rightarrow i=12A}$

$U=\frac{1}{2}L{i}^2=\frac{1}{2}*2*12^2=144J$

For JEE Main exam, the Electric Charges and Fields is an important chapter. It is a part of Electrostatics unit. The weightage of this unit is around 6-9% of the total Physics section. You should expect around 3-5 questions in this unit including the questions from the class 12 physics chapter 1.