UV-VIS SPECTROPHOTOMETRY

Question 1

• Technique used to measure the absorption of ultraviolet and visible light by molecules in a sample
• it provides information about the concentration and structure of molecules based on their absorbance characteristics in the uv invisible regions of the electromagnetic spectrum

Answer 1

UV-Vis spectrophotometry

Question 2

Basic principle:
____ and ____ comprise only a small part of the electromagnetic spectrum which includes such other forms of radiation as a radio, infrared, cosmic, and x-rays

Answer 2

Ultraviolet and visible radiation

Question 3

The energy associated with electromagnetic radiation is defined by the equation of:

Answer 3

e = hv, where
e - energy in joules
h- plank constant (6.62 x 10 ^ -34) joul-hertz or joule-second
v- is frequency in seconds

Question 4

Ultraviolet and visible radiation compromise only a small part of the electromagnetic spectrum which includes such other forms of radiation as radio, infrared, cosmic, and x-rays

Answer 4

THE ELECTROMAGNETIC SPECTRUM

Question 5

Electromagnetic radiation can be considered as a combination of alternating electric and magnetic fields that travel through space with a wave motion because radiation acts as a wave it can be classified in terms of either ____ or ___

Answer 5

Wavelength or frequency

Question 6

Wavelength and frequency are related by the equation:

Answer 6

v = c/λ, where
v - frequency in seconds
c - the speed of light (3 * 10 ^ 8 ms-1)
λ- wavelength in meters

Question 7

Electromagnetic radiation can be considered a combination of alternating electric and magnetic fields that travel through space in a wave motion.

Answer 7

Wavelength and frequency

Question 8

In general when measuring uv visible spectra we want only ___ to occur. Because light is a form of energy absorption of light by matter causes the energy content of the molecules to ___

Answer 8

Absorbance
Increase

Question 9

When light passes through or is reflected from a sample the amount of light absorbed is the difference between the ___ __ and ___ ___

Answer 9

incident radiation (Io) and the transmitted radiation (I)

Question 10

Transmittance equation

Answer 10

T=I/Io or T=I/Io x 100

Question 11

Absorbance equation

Answer 11

A=-logT

Question 12

Many spectrophotometers depending on the wavelength setting alternate between a halogen lamp for visible range and the deuterium lamp for the ultraviolet region

Answer 12

Light source

Question 13

Light source:
Many spectrophotometers depending on the wavelength setting alternate between a ____ lamp for visible range and the ___ lamp for the ultraviolet region

Answer 13

halogen
deuterium

Question 14

A device that disperses monochromatic from polychromatic light

Answer 14

Monochromator

Question 15

Monochromator is a device that disperses ___ from ____ light

Answer 15

monochromatic
polychromatic

Question 16

is the process of breaking down light into its constituent wavelengths in a manner similar to rainbow

Answer 16

Dispersion

Question 17

Tool used to separate the spectral lines

Answer 17

Diffraction grating

Question 18

Quartz __ are frequently used for ultraviolet measurement since many plastics and glass absorb uv light and cause interference

Answer 18

Cuvette (sample holder)

Question 19

The incoming light is transformed by ___ into a measurable electrical current

Answer 19

Detector

Question 20

General components

Answer 20

Light source
Monochromator
Cuvette
Detector

Question 21

Journal article

Answer 21

Determination of sun protection factor by uv-vis spectrophotometry

Question 22

Objective of the study

Answer 22

To determine the real spf value of the chemical or physical sunscreen through uv visible spectroscopy

Question 23

• Quartz is highly ____ to UV light, meaning it does not absorb UV wavelengths.
• This property allows the UV light to pass through the quartz cuvette without significant attenuation or interference

Answer 23

Transparent

Question 24

polychromatic light contains ___ wavelengths (colors) of light.

Answer 24

Multiple

Question 25

Inside the monochromator, there is a dispersive element, such as a:

Answer 25

prism
diffraction grating

Question 26

separates the different wavelengths of light based on their different angles of refraction

Answer 26

Prism

Question 27

separates the different wavelengths of light based on their different angles of diffraction

Answer 27

diffraction grating

Question 28

After the light is dispersed, it passes through an ____ ___. By moving the slit, the monochromator can isolate a specific wavelength of light, effectively selecting a narrow band of wavelengths (monochromatic light) from the dispersed spectrum.

Answer 28

Adjustable slit

Question 29

• the initial amount of light that strikes the sample.
• It represents the intensity of the light source before any interaction with the sample occurs.

Answer 29

Incident Radiation (I₀)

Question 30

• the amount of light that passes through the sample and emerges on the other side.
• It represents the intensity of light that is not absorbed by the sample.

Answer 30

Transmitted Radiation (I)