81.
What is the wavelength of visible spectrum ?

82.
Which layer of the earth's atmosphere reflect back the radio waves to the earth's surface ?

83.
Where are mesons found ?

85.
Which of the following has the lowest frequency?

86.
Which of the following is not true about X-rays?

87.
X–rays are

88.
X-rays region lies between

89.
In the absence of ozone layer, which rays will enter into atmosphere?

90.
In MRI machine, which one of the following is used?