Lifetimes of the molecules in the excited states are often measured by using pulsed radiation source of duration nearly in the nano-second range. If the radiation source has a duration of 2 ns and the number of photons emitted during the pulse source is 2.5 × 1015, calculate the energy of the source.
Solution and Explanation
Frequency of radiation, v = \(\frac{1}{2.0\times10^{-9}}\) s
= 5.0 × 108 s
Energy (E) of source = Nh\(\omega\)
Where N = number of photons emitted
h = Planck's constant
\(\omega\) = frequency of radiation
Substituting the values in the given expression of (E):
E = (2.5 × 1015) (6.626 × 10-34 Js) (5.0 × 108 s-1)
E = 8.282 × 1010 J
Hence, the energy of the source (E) is 8.282 × 1010 J.
Top CBSE Class XI Chemistry Questions
- Consider the following species: N3- , O2-, F-, Na+, Mg2+ and Al3+
- What is common in them?
- Arrange them in the order of increasing ionic radii.
- CBSE Class XI
- Chemistry
- Modern Periodic Law And The Present Form Of The Periodic Table
- Write the resonance structures for SO3 , NO2 and NO3-
- CBSE Class XI
- Chemistry
- Kossel-Lewis Approach to Chemical Bonding
- The concentration of sulphide ion in 0.1M HCl solution saturated with hydrogen sulphide is 1.0 × 10–19 M. If 10 mL of this is added to 5 mL of 0.04 M solution of the following: FeSO4, MnCl2, ZnCl2 and CdCl2. in which of these solutions precipitation will take place?
- CBSE Class XI
- Chemistry
- Law Of Chemical Equilibrium And Equilibrium Constant
- In the alkane \( H_3C-CH_2-C(CH_3)_2-CH_2-CH(CH_3)_2\) , identify 1°,2°,3° carbon atoms and give the number of H atoms bonded to each one of these.
- Enthalpies of formation of CO(g), CO2(g), N2O(g) and N2O4(g) are –110, – 393, 81 and 9.7 kJ mol-1 respectively. Find the value of ∆rH for the reaction.
\(N_2O_4(g) + 3CO(g) → N_2O(g) + 3CO_2(g)\)- CBSE Class XI
- Chemistry
- Enthalpy change
Top CBSE Class XI Atomic Models Questions
How many neutrons and protons are there in the following nuclei? \(_{6}^{13}\textrm{C}\), \(_{8}^{16}\textrm{O}\), \(_{12}^{24}\textrm{Mg}\), \(_{26}^{56}\textrm{Fe}\), \(_{38}^{88}\textrm{Sr}\).
- CBSE Class XI
- Chemistry
- Atomic Models
Write the complete symbol for the atom with the given atomic number (Z) and atomic mass (A)
(i) Z = 17, A = 35
(ii) Z = 92, A = 233
(iii) Z = 4, A = 9- CBSE Class XI
- Chemistry
- Atomic Models
Find the energy of each of the photons which (i) corresponds to light of frequency 3×1015 Hz. (ii) have a wavelength of 0.50 Å
- CBSE Class XI
- Chemistry
- Atomic Models
- A 25 watt bulb emits monochromatic yellow light of wavelength of 0.57µm. Calculate the rate of emission of quanta per second.
- CBSE Class XI
- Chemistry
- Atomic Models
- Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. Calculate the threshold frequency (ν0) and work function (W0) of the metal.
- CBSE Class XI
- Chemistry
- Atomic Models
Top CBSE Class XI Questions
- Consider the following species: N3- , O2-, F-, Na+, Mg2+ and Al3+
- What is common in them?
- Arrange them in the order of increasing ionic radii.
- CBSE Class XI
- Modern Periodic Law And The Present Form Of The Periodic Table
- Evaluate \(\lim_{x\rightarrow 5}\) f(x), where f(x) = |x|-5
- Write the resonance structures for SO3 , NO2 and NO3-
- CBSE Class XI
- Kossel-Lewis Approach to Chemical Bonding
- How many words, with or without meaning, can be formed using all the letters of the word EQUATION at a time so that the vowels and consonants occur together?
- CBSE Class XI
- permutations and combinations
- The concentration of sulphide ion in 0.1M HCl solution saturated with hydrogen sulphide is 1.0 × 10–19 M. If 10 mL of this is added to 5 mL of 0.04 M solution of the following: FeSO4, MnCl2, ZnCl2 and CdCl2. in which of these solutions precipitation will take place?
- CBSE Class XI
- Law Of Chemical Equilibrium And Equilibrium Constant
Concepts Used:
Structure of Atom
Atomic Structure:
The atomic structure of an element refers to the constitution of its nucleus and the arrangement of the electrons around it. Primarily, the atomic structure of matter is made up of protons, electrons and neutrons.
Dalton’s Atomic Theory
Dalton proposed that every matter is composed of atoms that are indivisible and indestructible.
The following are the postulates of his theory:
- Every matter is made up of atoms.
- Atoms are indivisible.
- Specific elements have only one type of atoms in them.
- Each atom has its own constant mass that varies from element to element.
- Atoms undergo rearrangement during a chemical reaction.
- Atoms can neither be created nor be destroyed but can be transformed from one form to another.
Cons of Dalton’s Atomic Theory
- The theory was unable to explain the existence of isotopes.
- Nothing about the structure of atom was appropriately explained.
- Later, the scientists discovered particles inside the atom that proved, the atoms are divisible.
Subatomic Particles
- Protons - are positively charged subatomic particles.
- Electron - are negatively charged subatomic particles.
- Neutrons - are electrically neutral particles and carry no charge
Atomic Structure of Isotopes
Several atomic structures of an element can exist, which differ in the total number of nucleons.These variants of elements having a different nucleon number (also known as the mass number) are called isotopes of the element. Therefore, the isotopes of an element have the same number of protons but differ in the number of neutrons. For example, there exist three known naturally occurring isotopes of hydrogen, namely, protium, deuterium, and tritium.