B2 Spectroscopic methods

Value of Planck's constant

• 6.634 x 10-34 J/s
• 1.609 x 10-19 Js
• 6.634 x 10-34 Js
• 9.66 x 10-31 J/s

If one substance has absorption peak at 510 nm, which colour of it can we observe?

• Yellow
• Green
• Violet
• Red

What is the wavenumber?

• number of waves per centimeter and is equal to 1/lamda
• Number of oscillation of the electric field vetor per unit time
• linear distance between successive maxima or minima of a wave

Which range of spectrum is in UV region

• 400 - 800 nm
• 200 - 800 nm
• 200 - 400 nm
• 100 - 200 nm

Which region of electromagnetic radiation is nonionizing

• X-ray
• Radiofrequencies
• Infra-red
• Gamma-rays
• Visible

The possible transitions for water molecule in UV-visible region are

• σ →σ*
• n→π*, π→π*
• σ→σ*, n→π*
• n → σ*

Atomic emission spectroscopy is

• The measurement of intensity of emitted  light at a particular wave length from the atoms that are exited thermally.
• The measurement of absorbance of emitted light at a particular wave length from the atoms that are exited thermally.
• The measurement of intensity of emitted light at a particular wave length from the atoms that are exited by monochromatic light.
• The measurement of intensity of absorbed light at a particular wave length from the atoms that are exited thermally.

What is absorption

• the electromagnetic waves are changed from propagating in one direction to all directions.
• Light which retained by a substance
• the surface returns a portion of the energy.
• light passes through space or the media

In fluorescence spectroscopy, emission spectra is obtained by keeping

• Emission wavelength constant
• Excitation wavelength constant
• Both excitation and emission wavelength constant
• Both excitation and emission wavelength varying

Which process is used for fluorescence spectroscopy

• A
• B
• C