Useful equations and constants hc h 6.626x 10* J.s c 2.998 x 10° m.s 1nm 10 m 1.

Question

Useful equations and constants hc h 6.626x 10* J.s c 2.998 x 10° m.s 1nm 10 m 1. Brilliant colors of fireworks are produced by the presence of different chemical compounds. Red color indicates the presence of lithium carbonate and blue color indicates the presence of copper chloride. a) What is the energy of a photon of red light that has a wavelength of 670 nm? Would the energy of a photon of blue light with a wavelength of 505 nm be higher or lower than a photon of red light? b) 2. Given below is a schematic diagram of the atomic structure proposed by Niels Bohr (Hence known as Bohr model). According to Bohr model positively charged nucleus is at the center and electrons travel around the nucleus in circular orbits. Each orbit represents an energy level and is designated by the value Larger the n number larger the energy. Each arrow represents electronic transition. Based on the length of the arrows, rank the following transitions in order of greatest change in electron energy to the smallest change. n- n- n- ucleu Largest energy change-->smallest energy change

Explanation / Answer

Solution :-

Q1) a) Lets calculate the energy of the red light photon with wavelength 670 nm

Converting nm to meter

670 nm*1m/1*10^9 nm = 6.70*10^-7 m

E= hc/l

E= 6.626*10^-34 J.s * 2.998*10^8 m s-1 / 6.70*10^-7 m

E = 2.96*10^-19 J

Therefore energy of the red light photon is 2.96*10^-19 J

b) calculating the energy of blue light with wavelength 505 nm

505 nm*1m/1*10^9 nm = 5.05*10^-7 m

E= hc/l

E= 6.626*10^-34 J.s * 2.998*10^8 m s-1 / 5.05*10^-7 m

E = 3.93*10^-19 J

The energy of the light photon is higher than energy of red light photon.

Q2)

As we can see the diagram showing the transition of electrons from one energy level to another energy level the largest energy change is shown by n3 ->n1

Smallest energy change is shown by n4->n3

Second highest is by n2 -> n1

Third highest is by n3 ->n2

Therefore order is as follows from highest to lowest

b > a> c > d

b)n=3 à n=1 > a) n=2 à n=1 > c) n=3 à n=2 > d) n=4à n=3

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