List of top Science Questions asked in CBSE Class X

Study the data given below showing the focal length of three concave mirrors A, B and C and the respective distances of objects placed in front of the mirrors:

Case	Mirror	Focal Length (cm)	Object Distance (cm)
1	A	20	45
2	B	15	30
3	C	30	20

(i) In which one of the above cases the mirror will form a diminished image of the object? Justify your answer.
(ii) List two properties of the image formed in case 2.
(iii) (A) What is the nature and size of the image formed by mirror C? Draw ray diagram to justify your answer.

OR

(iii) (B) An object is placed at a distance of 18 cm from the pole of a concave mirror of focal length 12 cm. Find the position of the image formed in this case.

In a domestic circuit five LED bulbs are arranged as shown. The source voltage is 220 V and the power rating of each bulb is marked in the circuit diagram. Based on the following circuit diagram, answer the following questions:

(a) State what happens when
(i) key K₁ is closed.
(ii) key K₂ is closed.
(b) Find the current drawn by the bulb B when it glows.
(c) Calculate
(i) the resistance of bulb B, and
(ii) total resistance of the combination of four bulbs B, C, D and E.
OR
(c) What would happen to the glow of all the bulbs in the circuit when keys K₁ and K₂ both are closed and the bulb C suddenly get fused ? Give reason to justify your answer.

Give reason for this: Fine hair and mucus are present in the nasal passage.

When 2 mL of sodium hydroxide solution is added to a few pieces of granulated zinc in a test tube and then warmed, the reaction that occurs can be written in the form of a balanced chemical equation as:

Select from the following a decomposition reaction in which the source of energy for decomposition is light:

A metal and a non-metal that exists in liquid state at the room temperature are respectively :

Carbon compounds :
(i) are good conductors of electricity.
(ii) are bad conductors of electricity.
(iii) have strong forces of attraction between their molecules.
(iv) have weak forces of attraction between their molecules.
The correct statements are :

Consider the following compounds:
FeSO₄ ; CuSO₄ ; CaSO₄ ; Na₂CO₃
The compound having the maximum number of water of crystallisation in its crystalline form in one molecule is:

Oxides of aluminium and zinc are :

MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂
The reaction given above is a redox reaction because in this case:

Consider the following statements:
(i) The sex of a child is determined by what it inherits from the mother.
(ii) The sex of a child is determined by what it inherits from the father.
(iii) The probability of having a male child is more than that of a female child.
(iv) The sex of a child is determined at the time of fertilisation when male and female gametes fuse to form a zygote.
The correct statements are:

Chromosomes:
(i) carry hereditary information from parents to the next generation.
(ii) are thread like structures located inside the nucleus of an animal cell.
(iii) always exist in pairs in human reproductive cells.
(iv) are involved in the process of cell division.
The correct statements are:

In a nerve cell, the site where the electrical impulse is transmitted to the next neuron is called:

A stomata closes when :
(i) it needs carbon dioxide for photosynthesis.
(ii) it does not need carbon dioxide for photosynthesis.
(iii) water flows out of the guard cells.
(iv) water flows into the guard cells.
The correct reason(s) in this process is/are :

At what distance from a convex lens should an object be placed to get an image of the same size as that of the object on a screen ?

The lens system of human eye forms an image on a light sensitive screen, which is called as :