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CBSE - 10th Study Notes
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3/10/2010 2:04:13 PM
Rajesh

icon 10Th Science Question - Answers
  Why does a ray of light bend when it travels from one medium into another?

Different media have different refractive indices. Due to this difference in the refractive indices, the speed of a light ray in one medium is different from its speed in another medium. Hence, a light ray bends on moving from one medium to another.

Why does sky look blue on a clear day?

Clear sky appears blue because among all the colours of white sunlight, the blue-coloured light gets scattered the most.

What are the two main components of our environment?

Biotic and abiotic factors are the two main components of our environment

What will happen to a plant if its xylem is removed?

Xylem is the water-conducting tissue of plants. If the xylem of a plant is removed, then the conduction of water will not take place. As a result, the plant will die

Name two tissues that provide control and coordination in multicellular animals

The two tissues that provide control and coordination in multicellular organisms are the nervous and muscular tissues.

What are natural resources? State two factors that work against an equitable distribution of these resources.

Natural resources are the resources present in nature, which can be used for our various needs. The examples of such resources are forests, wildlife, water, coal, petroleum, etc.
Two factors that work against the equitable distribution of these resources are:
(i) Human greed
(ii) Corruption and the lobby of the rich and the powerful


What is water harvesting? Mention any two water harvesting structures

Rainwater harvesting is the method of collecting rainwater for future use. Harvesting of rainwater is essential for ensuring the availability of usable water. The underlying concept is to make rainwater percolate below the ground, so that the level of groundwater gets replenished.
Khadins and Nadis are two water harvesting structures that are prominent in Rajasthan. Small pits, lakes, earthen dams, sand and limestone reservoirs, and rooftop water collecting units are some of the structures that are used for water harvesting.

What are ‘nastic’ and ‘curvature’ movements? Give one example of each

Nastic movements are non-directional movements that show response towards stimuli such as light, temperature, humidity, etc. The direction of nastic movements is independent of the direction of stimulus. Opening and closing of flowers is an example of photonastic response.

Curvature movements involve curving or bending of a plant in response to any stimuli. The curving of the stem tip towards light, due to the hormone auxin, is an example of curvature movement.

What is biogas? Why is biogas considered an ideal fuel for domestic use?

The gas made from the anaerobic digestion of agricultural and animal wastes is called biogas. When the biomass (agricultural and animal wastes) is decomposed in the absence of oxygen, it releases biogas.
Biogas is considered as an ideal fuel because it:
(i) Has a high calorific value
(ii) Produces no smoke on burning
(iii) Burns smoothly without any explosion
(iv) Leaves no residue on combustion


Explain analogous organs and homologous organs. Identify the analogous and homologous organs amongst the following:
Wings of an insect, wings of a bat, forelimbs of frog, forelimbs of a human.


Analogous organs: These are organs that have different origins, but perform similar functions.

Homologous organs: These are organs that are similar in origin (or are embryologically similar), but perform different functions.
The wings of an insect and those of a bat are examples of analogous organs.
The forelimbs of frog and those of a human are examples of homologous organs

Name a reducing agent that may be used to obtain manganese from manganese dioxide.

Aluminium (Al) is a reducing agent that may be used for obtaining manganese from manganese dioxide.

Why does tooth decay start when the pH of mouth is lower than 5.5?

Tooth enamel, which is made of calcium phosphate, is sensitive to pH.It does not dissolve in water (with neutral pH). However, it gets corroded when the pH inside the mouth is below 5.5. Hence, tooth decay starts when the pH of mouth is lower than 5.5

Why does a ray of light bend when it travels from one medium into another?

Different media have different refractive indices. Due to this difference in the refractive indices, the speed of a light ray in one medium is different from its speed in another medium. Hence, a light ray bends on moving from one medium to another

 
12/24/2012 3:49:03 PM
Ajay

icon Re: 10Th Science Question - Answers
  Name the largest artery in our body.

 
7/26/2014 10:31:59 PM
Abcd

icon Re: 10Th Science Question - Answers
  aorta

 
 
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