UV SPRECTROSCOPY MCQs:57

 UV SPRECTROSCOPY MCQs

 UV SPRECTROSCOPY MCQs

1. What is red shift

a. Shift of absorption of shorter wavelength

b. Shift of absorption exactly two times more the actual absorption

c. Shift of absorption to high energy

d. Shift of absorption to low energy

2. Which one is also known as Kayser

a. Per cm

b. Wavelength

c. x-ray

d. radio waves

3. What is a chromophore

a. Colored compound

b. Group of atoms in a compound responsible for abs. of EMR

c. Atoms that irradiate EMR

d. None

4. Which of the following is a principle chromophore in azo dye

a. N=N

b. C triple bond N

c. N triple bond N

d. C=N

5. A shift to lower wavenumber corresponds to

a. A shift to lower frequency

b. A shift to lower wavelength

c. A shift to higher energy

d. A loses if intensity

6. The color of a substance perceived by human eye is

a. Same as the substance meets in flam e

b. Same as the substance absorbs

c. Not same as the substance absorbs

d. Not same as the substance emits

7. Choose correct

a. IR has low wavenumber than visible light

b. Microwave has more energy than IR

c. UV has long wavelength than IR

d. IR has short wavelengththan visible

8. What is the instrument that measures the colored compound in solution?

a. Colorimeter

b. Coulometer

c. Colourmeter

d. Calorimeter

9. In which region EMR at 600 nm come

a. Visible

b. Vacuum

c. IR

d. Near

10. According to Beer lamberts law on which of the following does absorbance not depend

a. Distance that the light has travelled through the sample

b. Solution concentration

c. Extinction coefficient of sample

d. Color of solution

11. Sample cell used in UV-visible is

a. Glass

b. Quartz

c. Both

d. None

12. Suitable source of UV, except

a. Globar

b. Mercury arc

c. Tungsten

d. Xenon

13. In Beer Lambert’slaw A=ebc , c indicates

a. Concentration of compound in solution Expressed in mol/L

b. Cuvette path length

c. Molar concentration

d. Concentration of reference standard

14. Source of UV radiation is

a. Deuterium lamp

b. Carbon lamp

c. Mercury vapor lamp

d. None

15. Which is main limitation of beers law

a. Fluorescence

b. Analyte dissociation

c. Polychromatic radiation is used as a source

d. Analyte at high concentration

What is red shift?

Red shift refers to the shift of absorption to a longer wavelength (lower energy). This occurs when a molecule absorbs light at a lower energy level compared to its normal absorption.

What is Kayser known for in spectroscopy?

Kayser is associated with wavenumber measurement, commonly expressed in per centimeter (cm⁻¹), which is used in infrared (IR) spectroscopy.

What is a chromophore?

A chromophore is a group of atoms within a molecule that is responsible for the absorption of electromagnetic radiation (EMR), often leading to color formation in compounds.

What is the principal chromophore in azo dyes?

The N=N (azo group) is the principal chromophore responsible for the color in azo dyes.

What happens when a molecule shifts to a lower wavenumber?

A shift to a lower wavenumber corresponds to:

• Lower frequency
• Longer wavelength
• Lower energy absorption

Why is the perceived color of a substance different from what it absorbs?

The color of a substance that we see is not the same as the color it absorbs. Instead, we see the complementary color that is reflected or transmitted.

What is the relationship between different types of electromagnetic radiation?

Infrared (IR) has a lower wavenumber than visible light. Microwaves have less energy than IR. UV has a shorter wavelength than IR. IR has a longer wavelength than visible light.

Which instrument is used to measure colored compounds in a solution?

A colorimeter is used to measure the concentration of colored compounds in a solution based on absorbance.

In which region does electromagnetic radiation at 600 nm belong?

600 nm falls within the visible light spectrum, appearing as an orange-red color.

What factors do not affect absorbance in Beer-Lambert’s Law?

Absorbance does not depend on the color of the solution but is influenced by:

• Path length of light through the sample
• Concentration of the solution
• Extinction coefficient of the sample

What type of sample cell is used in UV-Visible spectroscopy?

Quartz cells are used in UV-Visible spectroscopy because they do not absorb UV light, unlike glass cells.

Which of the following is NOT a suitable source for UV light?

Globar is a source of infrared (IR) radiation and is not suitable for UV spectroscopy. Suitable UV sources include:

• Mercury arc lamp
• Tungsten lamp
• Xenon lamp

What does 'c' indicate in Beer-Lambert’s Law (A = εbc)?

‘c’ represents the concentration of the compound in solution, typically expressed in moles per liter (mol/L).

What is the most common source of UV radiation?

The deuterium lamp is a widely used source for UV radiation in spectroscopic analysis.

What is a major limitation of Beer’s Law?

A significant limitation of Beer’s Law is that it does not hold well at high concentrations, where deviations occur due to:

• Fluorescence of the sample
• Analyte dissociation
• Use of polychromatic radiation instead of monochromatic light