1. How is sound produced ?
Ans: Sound is produced by a vibrating body e.g. when a tightly stretched bond is plucked, it vibrates and produced sound. When it stops vibrating , it does not produced any sound . 2. How is sound produced by humans? Ans: In humans, the sounds is produced by the voice box or the larynx. Put your fingers on the throat and find a hard bump that seem to move when you swallow. This part of the body is known as the voice box. This is at the upper end of the wind pipe. Two vocal cords are stretched across the voice box or larynx in such a way that it leaves a narrow slit between them for the passage of air. When the lungs force air through the suit the vocal cords vibrate, producing sound. 3. why the voices of men, women and children are different. Ans: The vocal cords in men are about 20 mm long. In women these are about 15 mm shorter. Children have very short vocal cords. This is the reason why the voices of men, women and children are different. 4. What is oscillatory motion Ans: The to and fro motion of an object is known as vibration. This motion is also called oscillatory motion. The number of oscillations per second is called the frequency. It is expressed in hertz. Its symbol is Hz. Amplitude and frequency are important properties of any sound. 5. On what factor loudness of sound deepens on? Ans: Loudness is property of sound that distinguish loud sound from bass . The loudness of sound depends on its amplitude. It is proportional to the square of the amplitude of the vibration producing the sound. When the amplitude of vibration is large, the sound produced is loud. When the amplitude is small the sound produced is feeble. The loudness is expressed in a unit called decibel(dB). Above 80 dB the noise becomes physically painful. 6. What is pitch? Ans: It is the characteristics of sound distinguish shrillness and pitch of the sound. When the frequency of the vibration is higher, then the sound has a higher pitch. When the frequency of vibration is lower, then the sound has a low pitch. The frequency of the voice of a child is higher than that of an adult. The voice of a woman has higher frequency and is shriller than that of a man. 7. What is range of the frequency of audible sound ? Ans: The sounds of the frequencies less than about 20 vibrations per second (20 Hz) are called inaudible sounds or infrasonic. Such sound can not be detected by the human ear. The sound of frequencies higher than about 20,000 vibrations per second (20 kHz) are called the ultrasonic sound. For human ear, the range of audible frequencies is roughly from 20 to 20,000 Hz 8. Why are sound waves called mechanical waves? Ans: Sound waves force the medium particles to vibrate. because of the interaction of the particles present in that medium 9. What is SONAR? Ans: SONAR stands for Sound Navigation and Ranging and it works on the principle of reflection of sound waves. The SONAR technique is used to determine the depth of the sea and to locate under water hills, valleys, submarines, icebergs sunken ships etc. 10. What is the intensity of sound? Ans: The amount of sound energy passing each second through unit area is called the intensity of sound. 11. Define : (i) Reverberation of sound. (ii)Echo (iii) Time period (iv)Wavelength. (v) wave velocity (vi) compression. (vi) rarefaction Ans: (1)The persistence of sound due to repeated reflection and its gradual fading away is called reverberation of sound. (2) Echo is a repetition of sound due to the reflection of original sound by a large and hard obstacle. (3) Frequency is defined as the number of oscillations per second. The time taken by the wave for one complete oscillation of the density or pressure of the medium is called the time period, T. (4) The distance between two consecutive compressions or two consecutive rarefactions is called the wavelength. (5)The distance traveled by a wave in one second is called wave velocity. It depends upon the nature of the medium through which it passes. (6) The part or region of a longitudinal wave in which the density of the particles of the medium is higher than the normal density is known as compression. (7) The part or region of a longitudinal wave in which the density of the particles of the medium is lesser than the normal density is called a rarefaction. 13. What through and crest. The point of maximum positive displacement on a transverse wave is known as crest. The point of maximum negative displacement on a transverse wave is known as through.
43 Comments
![]() Book resource: Science power Class 8th Check point [Formative Assessment] 1. Define Afforestation? Answer: The practice of planting more and more trees is called Afforestation. 2. What is desertification? What causes desertification? Answer: The phenomenon of converting fertile land into desert is called desertification. Deforestation causes desertification. 3. What is the effect of deforestation on rainfall and climate? Answer: Deforestation increases temperature and wind velocity that reduce rainfall. These changes led to climate change. 4. What is wild life? Answer: Wild life is an area where organism lives in their natural habitat like dense forest, jungle and water bodies. 5. Give one difference between endangered and vulnerable? Answer: Endangered are those animals that are not likely survive and will soon extinct where as Vulnerable are those animal which are likely to move in endangered category in future. 6. What is Red Data Book? Answer: Red Data Book is the source book which keeps a record of all the endangered animals and plants. 7. Name the first national park of India? When it was it established? Answer: A national park is protected land area that provide natural habitat to wild life. Jim Corbett National Park is the first national park of India established in 1936. 8. Name three different region of biosphere reserve? Answer: Core Zone, Buffer Zone, and Manipulation Zone. 9. Name the international body responsible for wild life conservation? Answer: World Conservation union 10. What is the objective of project tiger? Answer: To save tigers from unauthorized killing. 11. What are endemic species? Answer: Endemic species are those species of plants and animals which are found exclusively in a particular area and do not found anywhere else naturally. Related posts for 8th Conservation of Plants and Animals Conservation of Plants and Animals Download File Check point[Formative Assessment] Download File Science power [Solved Assessment] Download File 1 MARKS QUESTIONS
1. A farmer floods his field everyday thinking that watering in this manner will result a better yield of his wheat crop. What will be the result of this action of the farmer. Ans.This will result in water logging of the soil due to which roots cannot breathe and ultimately plants will die . 2. Name the term for transport of food from leaves to other parts of plants. Ans.Translocation 3. Which pancreatic enzyme is effective in digesting proteins? Ans.Trypsin 4. Which enzyme is present in saliva breaks down starch? Ans.Salivary amylase. 5. After a vigorous exercise you may experience cramps in your leg muscles. Why does this happen? Ans.Accumulation of lactic acid 6. Name the organelle in which photosynthesis occurs. Ans.Chloroplast. 7. Name the type of blood vessels which carry blood from organs to the heart. Ans.Veins. 8. Name the respiratory structures of i.Mosquito ii)earth worm. Ans.i) mosquito—System of air tubes. ii)earth worm—moist skin. 9. Write the two functions of kidneys. Ans. Osmoregulation and excretion. 10. What are spiracles. Ans The holes found on the lateral side of insect‘s body.X X Trigonometry Introduction and identities Test Paper - 1
Download File X Trigonometry Introduction and identities Test Paper - 2 Download File X Trigonometry Introduction and identities Test Paper - 3 Download File X Trigonometry Introduction and identities Test Paper - 4 Download File X Trigonometry Introduction and identities Test Paper - 5 Download File Solved class 10 Trigonometry Introduction and identities Test Papers |
Blog SeaRCH Link
All
Join Us For Update |