English Medium इयत्ता ९ - CBSE Question Bank Solutions

Name the scientists who described the arrangement of electrons in an atom.

Which ancient Indian philosopher suggested that all matter is composed of very small particles ? What
name was given by him to these particles ?

‘If 100 grams of pure water taken from different sources is decomposed by passing electricity, 11 grams of hydrogen and 89 grams of oxygen are always obtained’. Which chemical law is illustrated by this statement?

Name the central part of an atom where protons and neutrons are held together.

What are the various letters used by Bohr to represent electron shells in an atom?

Fill in the blanks with suitable words.
 A sound wave consists of places of higher pressure called ................. and places of................pressure called.................

Describe Bohr's model of the atom. How did Neils Bohr explain the stability of atom?

What is the difference between infrasonic waves and ultrasonic waves ?

Choose the infrasonic waves and ultrasonic waves from the following frequencies : 
(i) 10,000 Hz
(ii) 30,000 Hz
(iii) 18 Hz
(iv) 50,000 Hz
(v) 10 Hz 

What is the frequency range of hearing in humans ?

Which of the following sound frequencies cannot be heard by a human ear ?

(i) 10 Hz
(ii) 100 Hz
(iii) 10,000 Hz
(iv) 15 Hz
(v) 40,000 Hz 

What is ultrasound ? What is the  difference between ordinary sound and ultrasound ?

What are infrasonic waves ? Name two animals which produce infrasonic waves.

What are ultrasonic waves ? Name two animals which can produce ultrasonic waves.

The audible range of frequencies of an average human ear is from 20 Hz to 20 kHz. Calculate the corresponding wavelengths. (Speed of sound in air is 344 ms^–1)