Distinguish between loudness and intensity of sound.
[question] Question. Distinguish between loudness and intensity of sound. [/question] [solution] Solution: Intensity is an objective property of the sound wave. In fact, it is related to the square of the wave amplitude, and does not depend on the particular characteristics of a person’s ears. The amount of sound energy passing each second through unit area is called the intensity of sound. Loudness, on the other hand, is a subjective property of the sound that depends on the human ear, the sens...
Read More →Project/Activity
[question] Question. Project/Activity Solve this crossword puzzle with the help of the given clues. Across 1. Nagarjuna Sagar is a river valley project. Name the river? 2. The longest river of India. 3. The river which originates from a place known as Beas Kund. 4. The river which rises in the Betul district of MP and flows westwards. 5. The river which was known as the “Sorrow” if West Bengal. 6. The river on which the reservoir for Indira Gandhi canal has been built. 7. The river whose source ...
Read More →What is geothermal energy ?
[question] Question. What is geothermal energy ? [/question] [solution] solution: The heat energy inside the earth's crust is known as geothermal energy. The geological changes in some regions push the hot magma upwards which gets collected at some depth below the surface of earth. Such places are called hot spots. These hot spots serve as a source of heat energy (or geothermal energy). The geothermal energy is utilised to convert water into steam which rotates a steam turbine. [/solution]...
Read More →A person is listening to a tone of 500 Hz sitting at a distance of 450 m from the source of the sound.
[question] Question. A person is listening to a tone of 500 Hz sitting at a distance of 450 m from the source of the sound. What is the time interval between successive compressions from the source ? [/question] [solution] Solution: The time interval between two successive compressions is equal to the time period of the wave. It has nothing to do with the distance (450 m) of the person from the source. Time interval $=\frac{1}{\text { Frequency }}=\frac{1}{500}=2 \times 10^{-3} \mathrm{~s}$ [/so...
Read More →In what respects is the criterion used by the UNDP for measuring development different from the one used by the World Bank?
[question] Question. In what respects is the criterion used by the UNDP for measuring development different from the one used by the World Bank? [/question] [solution] Solution: The criterion used by the UNDP for measuring development is different from the one used by the World Bank in the sense that it uses a combination of factors such as health, education and income as indicators of development. It does not rely solely on per capita income, as is the case with the World Bank. [/solution]...
Read More →What are the limitations of energy
[question] Question. What are the limitations of energy that can be obtained from the oceans ? [/question] [solution] solution: The energy obtained from the oceans is (1) tidal energy, for which very few suitable sites are available for construction of dams and the generation is intermittent and not very large. (2) sea-waves energy, where power output is variable and the currently available technologies are quite expensive. (3) ocean thermal energy, where the conversion efficiency is quite low b...
Read More →Why are rivers important for the country’s economy?b
[question] Question. Why are rivers important for the country’s economy? [/question] [solution] Solution: Rivers have been of fundamental importance throughout human history. Rivers, lakes, ice caps, ground water are the fresh water reserves of the Earth. Water is a basic natural resource, essential for various human activities. The water from the rivers is used for various domestic, industrial and agricultural purposes. The presence of rivers boosts trade and commerce by helping in the easy tra...
Read More →What is the main criterion used by the World Bank in classifying different countries?
[question] Question. What is the main criterion used by the World Bank in classifying different countries? What are the limitations of this criterion, if any? [solution] Solution: The main criterion used by the World Bank in classifying different countries is the per capita income or average income of a person in a country. Limitations of this criterion: It does not tell us about how this average income is distributed among the people in the individual countries. Two countries with the same per ...
Read More →What kind of mirror - concave,
[question] Question. What kind of mirror - concave, convex or plane - would be best suited for use in a solar cooker ? Why? [/question] [solution] solution: A concave mirror is best suited for use in a solar cooker. This is because a concave mirror concentrates solar energy from over a large area into a small area (at its focus). As a result, high temperatures can be achieved. Such a mirror is called solar concentrator. [/solution]...
Read More →Calculate the wavelength of a sound wave whose frequency is 220 Hz
[question] Question. Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is 440 ms–1 in a given medium. [/question] [solution] Solution: Given, frequency, $v=220 \mathrm{~Hz}$; speed of sound, $\mathrm{v}=440 \mathrm{~ms}^{-1}$ Speed, $v=v \lambda \quad$ or $\quad \lambda=\frac{v}{v}=\frac{440}{220}=2 \mathrm{~m}$ [/solution]...
Read More →Compare the east-flowing and the west-flowing rivers of the Peninsular Plateau.
[question] Question. Compare the east-flowing and the west-flowing rivers of the Peninsular Plateau. [/question] [solution] Solution: [/solution]...
Read More →How has the traditional use of wind and water
[question] Question. How has the traditional use of wind and water energy been modified for our convenience ? [/question] [solution] solution: The traditional use of wind energy has been modified by using windmills (or wind turbines) and that of water by constructing hydro power plants. [/solution]...
Read More →Assume there are four families in a country. The average per capita income of these families is Rs 5000.
[question] Question. Assume there are four families in a country. The average per capita income of these families is Rs 5000. If the income of three families is Rs 4000, Rs 7000 and Rs 3000 respectively, what is the income of the fourth family? (i) Rs 7500 (ii) Rs 3000 (iii) Rs 2000 (iv) Rs 6000 [/question] [solution] Solution: (iv) Rs 6000 [/solution]...
Read More →Why are we looking at alternate sources of energy?
[question] Question. Why are we looking at alternate sources of energy? [/question] [solution] solution: Fossils fuels were formed due to extraordinary circumstances that took place millions of years ago. No new reservoirs of these fuels are being formed due to the absence of those circumstances. Thus, they are non-renewable sources of energy. If we continue to use these sources at the present rate, we would soon be deprived of these sources. That is why, we are looking for alternate sources of ...
Read More →Discuss the significant difference between the Himalayan and the Peninsular rivers.
[question] Question. Discuss the significant difference between the Himalayan and the Peninsular rivers. [/question] [solution] Solution: Apart from their difference of origin, the Himalayan and the Peninsular rivers are different from each other in many ways. However, the significant difference between them is that while the Himalayan rivers are perennial rivers, the Peninsular rivers are seasonal. The Himalayan rivers have water throughout the year. They receive water from rain as well as from...
Read More →Which of the following neighbouring countries has better performance in terms of human development than India?
[question] Question. Which of the following neighbouring countries has better performance in terms of human development than India? (i) Bangladesh (ii) Sri Lanka (iii) Nepal (iv) Pakistan [solution] Solution: (ii) Sri Lanka [/solution]...
Read More →How are the wavelength and frequency of a sound wave related to its speed ?
[question] Question. How are the wavelength and frequency of a sound wave related to its speed ? [/question] [solution] Solution: Speed of sound = frequency × wavelength [/solution]...
Read More →Below are given names of a few lakes of India.
[question] Question. Below are given names of a few lakes of India. Group them under two categories − natural and created by human beings. (a) Wular (b) Dal (c) Nainital (d) Bhimtal (e) Gobind Sagar (f) Loktak (g) Barapani (h) Chilika (i) Sambhar (j) Rana Pratap Sagar (k) Nizam Sagar (l) Pulicat (m) Nagarjuna Sagar (n) Hirakud [/question] [solution] Solution: [/solution]...
Read More →What are the disadvantages of fossil fuels ?
[question] Question. What are the disadvantages of fossil fuels ? [/question] [solution] solution: Fossil fuels (coal, petroleum and natural gas) have the following disadvantages : (1) The fossil fuels are non-renewable sources of energy, if we continue to consume these sources at alarming rates, we would soon run out of energy. (2) There are no such alternate sources of energy developed till today which can replace fossil fuels. Thus, large dependency on fossil fuels for most of our energy requ...
Read More →What are wavelength, frequency,
[question] Question. What are wavelength, frequency, time period and amplitude of a sound wave ? [/question] [solution] Solution: Wavelength : It is the distance between two consecutive compressions or two consecutiv rarefactions. Frequency : The number of compressions or rarefactions taken together passing through a point in one second is called frequency. Time Period : It is the time taken by two consecutive compressions or rarefactions to cross a point. Amplitude : It is the magnitude of maxi...
Read More →Development of a country can generally be determined by
[question] Question. Development of a country can generally be determined by (i) its per capita income (ii) its average literacy level (iii) health status of its people (iv) all the above [solution] Solution: (i) its per capita income [/solution]...
Read More →If you could use any source of energy for heating your food,
[question] Question. If you could use any source of energy for heating your food, which one would you use and why ? [/question] [solution] solution: We would use a microwave oven for heating the food as it heats uniformly and cleanly without loss in its nutritional value. Also, we can use solar cooker if bright sunlight is available because the nutrients are not lost during heating in solar cooker. [/solution]...
Read More →Answer the following questions briefly.
[question] Question. Answer the following questions briefly. (i) What is meant by a water divide? Give an example. (ii) Which is the largest river basin in India? (iii) Where do the rivers Indus and Ganga have their origin? (iv) Name the two headstreams of the Ganga. Where do they meet to form the Ganga? (v) Why does the Brahmaputra in its Tibetan part have less silt, despite a longer course? (vi) Which two Peninsular rivers flow through trough? (vii) State some economic benefits of rivers and l...
Read More →What is a good fuel ?
[question] Question. What is a good fuel ? [/question] [solution] solution: (1) It should have a high calorific value [calorific value is defined as the number of heat units produced when unit mass of fuel is burnt] Thus, a good fuel should liberate more heat per unit mass. (2) It should have low moisture content. (3) It should have low non-combustible matter like ash, etc. That is, it should leave low ash and other residual matter after combustion. (4) Its products of combustion should not be h...
Read More →What is a good source of energy ?
[question] Question. What is a good source of energy ? [/question] [solution] solution: A good source of energy should be (1) Capable of doing large amount of work per unit mass or volume. (2) Easily accessible i.e., it should be convenient to use. (3) Easy to transport and store. (4) Capable of delivering desired quantity of energy at a steady rate over a long period of time. (5) Should be economical. [/solution]...
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