Energy of an electron is given by
E =- 2.178 x 10^-18 J 
Wavelength of light required to excite an electron in a hydrogen atom from level n =1 to n=2 will be (h=6.62 x 10³⁴ Js and c = 3.0 x 10⁸ ms^-1) 

• 1.214 x 10^-7 m

• 2.816 x 10^-7 m

• 6.500 x 10^-7 m

• 8.500 x 10^-7

Who discovered neutron?

What is the name of the remaining part of atom except outer orbit?

Name the particles which determine the mass of an element.

What are α-particles?

What are the fundamental particles present in a neutral atom having atomic number greater than 1?

Do protons and neutrons have identical mass?

When α-particles are sent through a thin metal foil, most of them go straight through the foil. What inference do you draw from it?