Question

EXPERIMENT #9: EMISSION SPECTROSCOPY PRE-LAB NAME DATE STD # SEQUENCE # 1. When electricity is passed through gases such as hydrogen or neon, certain colors are emitted. What occurs in an atom to produce these colors? 2. (a) Calculate the frequency (v) of light that has a wavelength) of 3.00 x 104 cm. (Show calculation) (b) Calculate the energy of this light wave. (Show calculation) 3. State TWO differences between light from a laser and light from a flashlight 4. Which type of electromagnetic radiation carries the most energy?

Answer 1

1) When an electric current passes through gases like hydrogen or neon,the electrons of atoms of gases absorbs energy and get excites to higher energy levels and after some time they moveback into lower energy levels by releasing energy which will be in the range of viscible spectrum and hence they will show colors.

ex; Gas discharge lamps of hydrogen ,fluorecent neon lamps.

2)a We can use the equation ,

frequency( $\upsilon$ ) = Velocity(C) / wavelength( $\lambda$ )

= 3.0 x 10⁸ cm/s / 3 x10^-4 cm = 10000 Hz

2)b We can use plank-einstein equation to calculate energy of the light wave as

Energy of light (E) = plank's costant x frequency of light ($\upsilon$)

= 6.626 x 10^-34 J.s x 10000 Hz = 6.626 x 10^-30 J

3) Ordinary light(flash light) is not strictly a monochromatic as it travels in form of short pulses of small length and short duration .wavelength range-400 to 700nm

Laser light is strictly monochromatic as it travels in the form of large lengths and long duration.only one wavelength is used.

Intensity of ordinary light decreases with distance as it travels in short pulses of small lengths and short duration.

The intensity of laser light remains very long distances as it travels in only one direction ,which is parllel to the optic axis.

4) The increasing order of enegy of electromagnetic radiation from left to right as

Radio waves < micro waves < IR < Visible < UV < X-rays < Gamma rays

Answer : Gamma rays