List of top Science Questions asked in CBSE Class X

State reason of bending of the refracted ray away from the normal. 

Out of the two Media – Medium 1 and Medium 2, in which is the speed of light more?

Explain the mechanism of inheritance used by sexually reproducing organisms to ensure the stability of DNA of the species. 

A doctor finds in one of his patients that he is not maintaining a proper posture and balance of his body. State the region of brain and also the part of the brain which is responsible for it. 

How is the brain protected in our body? 

A light green coloured solution of sulphate salt of metal 'P' is taken in a beaker, a rod of another metal 'Q' is put in this solution as shown in the following figures: 

Assertion (A): Food web is a network of several food chains operating in an ecosystem. 
Reason (R): Food web decreases the stability of an ecosystem.

Assertion (A): In the common domestic circuit, the earth wire is connected to a metallic plate buried deep inside the earth. 
Reason (R): Earth wire ensures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth, so the user may not get a severe electric shock.

Assertion (A): Xylem tissue moves water and minerals obtained from the soil by the roots. 
Reason (R): Xylem tissue is found only in the roots of a plant. 

Assertion (A): Carbon and its compounds are our major sources of fuels. 
Reason (R): Most of the carbon compounds on burning release a large amount of heat and light.

The incorrect statement about ozone is: 

Consider the following food chain: Grass → Grasshopper → Frog → Snake → Eagle If the amount of energy available at third trophic level is 50 kJ, the available energy at the producer level was: 

The part of human eye which controls the amount of light entering into it is:

Identify from the following the ray diagram which shows the correct path of the reflected ray for the ray incident on a concave mirror as shown:

In human alimentary canal, the digestive juice secreted by the gastric glands are: 

The basic filtration unit of the excretory system in human beings is:

Select the option having correct matching of the organism given in Column I with the mode of reproduction in Column II: Column I {0.2cm}

A pair of endocrine glands located in the human brain is:

The water of crystallization is present in:

Juice of tamarind turns blue litmus to red. It is because of the presence of a chemical compound called: 

The colour of the solution observed after about 1 hour of placing iron nails in copper sulphate solution is: 

A hydrocarbon which does not belong to the same homologous series of carbon compounds is

Select from the following a statement which is not true about the burning of magnesium ribbon in air:

You have three aqueous solutions A, B, and C as given below: 
A - Potassium nitrate 
B - Ammonium chloride 
C - Sodium carbonate 
The ascending order of the pH of these solutions is: