Arrange the following electromagnetic
radiations per quantum in the order of
increasing energy :
A : Blue light B : Yellow light
C : X-ray D : Radiowave.
C, A, B, D
B, A, D, C
D, B, A, C
A, B, D, C
MCQ (Single Correct Answer)
JEE Main 2017 (Offline)
An observer is moving with half the speed of light towards a stationary microwave source emitting waves
at frequency 10 GHz. What is the frequency of the microwave measured by the observer? (speed of light =
3 ×108 ms–1)
This question is from Doppler's effect of light.
When observer is moving towards the source then the frequency of wave measured by the observer will be
In a Young’s double slit experiment, slits are separated by 0.5 mm, and the screen is placed 150 cm away.
A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes
on the screen. The least distance from the common central maximum to the point where the bright fringes
due to both the wavelengths coincide is
Let n1th fringe formed due to first wavelength and n2th fringe formed due to second wavelength coincide. So their distance from common central maxima will be same.
A diverging lens with magnitude of focal length 25 cm is placed at a distance of 15cm from a converging
lens of magnitude of focal length 20cm. A beam of parallel light falls on the diverging lens. The final
image formed is:
real and at a distance of 6 cm from the convergent lens.
real and at a distance of 40 cm from convergent lens.
virtual and at a distance of 40 cm from convergent lens.
real and at a distance of 40 cm from the divergent lens.
As parallel beam incident on diverging lens so the image will be formed
at the focus of diverging lens.
$$ \therefore $$ v = –25 cm
The image formed by diverging lens is used as an object for