<h2>Answer: Ultraviolet Light
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Ultraviolet light, whose wavelength is approximately between 100 nm and 380 nm; is a type of electromagnetic radiation that is not visible to the human eye.
This light is used for many purposes, among which is the identification of fluerescent minerals.
In this sense, fluorescence is a property that certain materials have in which they absorb energy in the form of short wavelength not visible electromagnetic radiation (the ultraviolet, for example) and then emit some of that energy in the form of longer wavelength electromagnetic radiation (in the visible spectrum). This is also called luminiscence.
Hence, the correct option is a.
Answer:
April to June
Explanation:
Not really an explanation, I just know it.
Speed of wave = frequency x wavelength
= 250 x 6 = 1500 m/s.
Answer:
Explanation:
Given
mass of cylinder is M
radius R
velocity of center of mass is v
As there is no slipping therefore cylinder will rotate as well as translate
Moment of inertia of cylinder 
Kinetic Energy of cylinder 
Rotational energy 
for rolling

where 

Total kinetic Energy 
Using the law of conservation of momentum
m1u1+m2u2=m1v1+m2v2
Where m1 is mass of first object
m2 is mass of second object
u1 and u2 are initial velocities of object 1 and 2 respectively
v1 and v2 are final velocities of object 1 and 2 respectively
Here, they are moving as a system after collision. Thus they will posses same final velocity
m1u1 +m2u2=v(m1+m2)
Substituting values
600*4+0=v(600+400)
2400=v*1000
v=2.4 m/s
Now momentum of system
p=Mv
p=(600+400)*2.4
p=1000*2.4
Therefore p=2400 kg m/s
Hope this helps :)