# 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 2023-24 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 2023-2024

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

#### Answer : 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

#### Question 2. The size of bacteria is 1 µ. Find the number of bacteria present in 1 m length.

Answer : 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

#### Question 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

#### Question 4. The wave length of light is 589 nm. What its wavelength in Å ?

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

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

Answer : 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.

#### Question 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.

Answer : 1 Min= 60 sec So 8 Min= 8×60 = 480 sec

Now distance = Speed×Time

= 3×108×480

=1.44×108 Km/s

#### Question 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.

Answer : 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 Me

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