RADIOACTIVITY

Q1: What is radioactivity?

A:  The  phenomenon of spontaneous emission of alpha particle or beta particle and gamma rays  from an unstable nucleus is called radioactivity. 

 Q2: When does a nucleus  become unstable ?

A: When the number of neutrons become much more than that of protons.

Q3: Which part of the atom takes part in radioactivity ?

A: Nucleus

Q4: What happens to the radioactive behaviour of a radioactive sample if it is chemically oxidized ?

A: The radioactive behaviour does not change. As oxidation is the chemical change, it does not affect the nuclear activity.

Q5: How does the atomic number and mass number change if a radioactive nucleus releases one alpha particle ?

A: Atomic number decreases by 2 and mass number decreases by 4

Q6: How does the atomic number and mass number change if a radioactive nucleus releases one beta particle?

A: Atomic number increases by 1 and mass number does not change.

PENDULUM ON MOON

Q. If a simple pendulum is taken to the moon from the earth without changing the length, what is the effect on it's time period?

Ans: As the time period of a simple pendulum is inversely proportional to the square root of acceleration due to gravity and the acceleration due to gravity of the moon is less than that of the earth, time period increases (square root of 6 times)

FORCE ON CURRENT CARRIYING CONDUCTOR

 Q: Why does a current carrying conductor placed in an magnetic field experiences force ?

Ans: Moving charges experience force in magnetic field. So when a current carrying conductor is placed in the magnetic field,it experiences force due to the force on moving charges inside it.

The formula F=IBLsin@, I= Current,  B =external magnetic field 

L is the length of conductor inside the magnetic field.

MAXIMUM FORCE

When the  conductor is placed perpendicular to the magnetic field.

MINIMUM FORCE

When the conductor is placed parallel to the magnetic fields 

SUBJECTIVE AND OBJECTIVE PROPERTIES OF A SOUND

 Question: What are subjective and objective properties of sound ?

Answer : Subjective properties are basically the properties which can be measured directly. Loudness, pitch (shrillness) and quality(Timbre) of sound are subjective properties. But these properties  are related to the the measurable quantities  called objective properties. 

Objective properties are the properties which can be measured. Intensity,  Amplitude, frequency, wavelength,  time period, intensity, fundamental frequency,  subsidiary frequencies are objective properties. 

Loudness depends on amplitude,  intensity of the sound.

Pitch(shrillness) depends on frequency.

Quality (Timbre) depends on waveform( combination of primary and subsidiary notes).

LOUD SOUND IS HEARD DURING RESONANCE

 QUESTION: Why is loud sound heard at RESONANCE?

 ANSWER: Loud sound is heard at RESONANCE because  amplitude increases when external  frequency is equal or integral multiple of the natural frequency of vibrating body.

EFFECTIVE COOLANT - WATER

Water has high specific heat capacity 4200J/(Kg°C) so it can absorb large amount of heat without much rise in it's own temperature.

ISLANDS ENJOY MODERATE CLIMATE

 Islands or coastal areas enjoy moderate climate. Why?

Ans. Water has higher heat specific capacity than the land due to which there is the continuous formation of sea breeze and land breeze near the coastal areas. This keeps the temperature moderate.

PRINCIPLE OF CALORIMETRY

If no heat is exchanged with surrounding, heat lost by the hot body is equal to heat gained by the cold body. 

70 to 80% water in plants and animals. Why?

Plants and animals have 70-80% water so that they can maintain body temperature as water has high specific heat capacity.

FARMERS FILL THEIR FIELDS WITH WATER.

Farmers fill their crop fields with water to protect from frost: why?

Water has high specific heat capacity so it delays the surrounding temperature to fall to zero degree Celsius ,thus protecting the crops from frost

FOMENTATION

Why is water used in fomentation ?

Water has high specific capacity due to which it cools slowly and imparts large amount of heat to our body.

ICSE ISC SEM 1 NOV 2021 EXAMINATION POSTPONED

ICSE and ISC semester 1 exams to be held in November 2021 is postponed. New datesheet will be released later.  It is now assumed that exam will be in offline mode.

REVISION QUESTIONS CLASS 10

PHYSICS REVISION TEST

CLASS 10 , MACHINESS AND REFRACTION OF LIGHT

ATTEMPT ALL QUESTIONS. 

Q1. Give two reasons for a  single movable pulley not to be 100% efficient. 2

Q2. What is the purpose of a Jack in lifting a car by it ? 2

Q3. Stars twinkle in the sky . Give reason.  2

Q4. Draw a labelled diagram of a block and tackle system with velocity ratio 5.     2

Q5 Name the single pulley with mechanical advantage more than one. State  its one disadvantage.2

Q6. State two laws of refraction 2

Q7 State two factors affecting refractive index of a medium. State the effect also.2

Q8. Which colour out of green and orange , is deviated the most. Give reason for your answer. 2

Q9. A water pond appears 1.35 m deep. If the refractive index of water is 4/3, find the actual depth of the pond. 2

Q10. What is total INTERNAL reflection?  2

Q11.Draw a diagram for the deviation of a light ray by 90°. 2

Q12 Which colour of the visible light has maximum critical angle.? Why? 2

Q13Explain the cause for sparkling of  a diamond. 2

Q14. Statr the principle of a simple machine. From which law is it derived? 2

Q15. State the principle of machines. 2