Measurements and Experimentation Exe-1A Numericals of Physics for ICSE Class-9 Selina Publishers

Measurements and Experimentation Exe-1A System of Unit Numericals for ICSE Class-9 Concise Selina Publishers. There is the solutions of Numericals Questions of your latest textbook which is applicable in 2025-26 academic session. Visit official Website CISCE for detail information about ICSE Board Class-9.

Measurements and Experimentation Exe-1 A System of Unit Numericals Questions Solutions

ICSE Physics for Class-9  Concise Selina Publishers

Board ICSE
Class 9
Subject Physics
Writer / Publication Concise selina Publishers
Chapter-1 Measurements and Experimentation 
Exe – 1 A System of Unit
Topics Solution of Exe-1(A) Numericals
Academic Session 2025-2026

System of Unit numericals problems / questions for practice, conversion of  one unit into other unit in very simple and easy way. Therefore practice these important questions/ problems to learn conversion of unit in effective way.

Exe-1A System of Unit Numericals

Measurements and Experimentation in Physics for ICSE Class-9 of  Concise Selina Publishers Chapter-1

Page 11

Que-1: The wavelength of light of a particular colour is 5800 Å. Express it in (a) nanometre and (b) metre.

Ans: Wavelength of light of particular colour = 5800 Å
(a) 1 A   = 10-1 nm
5800 A    = 5800 × 10-1 nm
= 580 nm
(b) 1 A  = 10-10 m
5800  A= 5800 × 10-10 m
= 5.8 × 10-7 m

Que-2: The size of bacteria is 1 µ. Find the number of bacteria present in 1 m length.

Ans: Size of a bacteria = 1 µ ,  Since 1 µ = 10-6 m
Number of the particle = Total length/size of one bacteria
= 1 m/10-6 m = 106

Que-3: The distance of a galaxy is 5·6 × 1025 m. Assuming the speed of light to be 3 × 108 m s “. Find the time taken by light to travel this distance .

[Hint : Time taken = distance/speed   ]

Answer : Distance of galaxy = 5.6 × 1025 m and Speed of light = 3 × 108 m/s
(a) Time taken by light = Distance travelled/speed of light
= (5.6 × 1025 / 3 × 108) s
= 1.87 × 1017 s

Que-4: The wave length of light is 589 nm. What its wavelength in Å ?

Ans: 1 nm= 10 Å Therefore 589 nm = 10×589A°= 5890 Å

Que-5: The distance of the nearest star, Proxima Centauri, from the Earth is 4.0 x 1013 km. Express it in light year.

Ans: 1 Light year = 9.46 x 1012 km
or 9.46 x 1012 km = 1 Light year
∴ 4.0 x 1013 km
= 1/(9.46×1012) x 4.0 x 1013
= 4.2 light years.

Que-6: It takes time 8 min for light to reach form the sun to the earth surface . If speed of light is taken to be 3 × 108 m/s, find the distance from the sun to the earth in km.

Ans: 1 Min= 60 sec So 8 Min= 8×60 = 480 sec
Now distance = Speed×Time
= 3×108×480
=1.44×108 Km/s

Que-7: ‘The distance of a star form the earth is 8.33 light minutes .’ What do you mean by this statements ? Express the distance in meter.

Ans: It means light take 8.33 Minute  to reach the star while the speed of light is 3×108 m/s.

Distance= Speed × Time
= 3×108 × 8.33×60
=1.5×1011Mitre

—  : End of Measurements and Experimentation Exe-1A System of Unit Numericals for ICSE Class-9 Concise Selina Publishers :–

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