Question

please send me important question of science cbse board 10th class

Answer 1

How may male gametes are produced by pollen grains?
Name the largest artery in the human body.
By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristic?
Ga, Ge, As, Se, Be
Light is incident at an angle of
(i)
30
0
300

(ii)
45
0
450
, on the same face of a given rectangular slab. If the angles of refraction, at this face are
r
1
r1
and
r
2
r2
in the two cases. Obtain the relation in these angles?
State the important uses of solar cells.
(a) An aqueous solution has a PH value of 7.0. Is it acidic, basic or neutral?
(b) If H+ concentration of a solution is
1×
10
–2
1×10–2
mol L-1 what will be its P4 value?
(c) Which has higher PH value: 1 – M HCl or 1 – M NaOH
OR
Draw ray diagram showing the image formation by a concave mirror when an object placed at centre of curvature of the mirror.
What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series?
How can three resistors of resistance 2
Ω
Ω
, 3
Ω
Ω
and 6
Ω
Ω
be connected to give a total resistance of (i) 4
Ω
Ω
, (ii) 1
Ω
Ω
?
Write two major shortcomings of Mendeleev’s periodic table? How have these been removed in the modern periodic table?
Describe double circulation in human beings. Why is it necessary?
OR
Draw ray diagram showing the image formation by a convex lens when an object is placed at infinity.
Outline a project which aims to find the dominant coat colour in dogs.
A change in DNA that is useful for one property to start with, can become useful later for a different function. Explain.
Why is respiration considered as an exothermic reaction? Explain.
OR
Draw ray diagram showing the image formation by a convex lens when an object is placed at twice the focal length of the lens.
A truck uses a convex mirror as view finder whose radius of curvature is 2.0 m. A maruti car is coming behind the truck at a distance of 10 m. What will be the position of the image of the car and size of the image of the car when observed by the driver of the truck through the convex mirror?
What are the major factors responsible for population explosion?
Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?
(a) Why does carbon form large number of compounds?
(b) Why are some of these called saturated and others are called unsaturated compounds?
(c) Which of these two is more reactive?
(d) Write the names of the following compounds:
C
H
3
–C
H
2
–Br
CH3–CH2–Br

C
H
3
−C
H
2
−C
H
2
−C
H
2
−C≡CH
CH3−CH2−CH2−CH2−C≡CH
OR
Draw ray diagram showing the image formation by a convex lens when an object is placed between optical centre and focus of the lens.
How phototropism does occur in plants?
(a) What is myopia? State the two causes of myopia. With the help of labelled ray diagrams show
(i) the eye defect myopia
(ii) correction of myopia using a lens.
(b) Why is the normal eye can’t focus on an object placed within 10cm from eye?
An ore on treatment with dilute hydrochloric acid gives a smell like that of rotten eggs. What type of ore is this? How can it be concentrated? How can the metal be obtained from the concentrated ore?
Describe how ozone layer is formed.
OR
Draw ray diagram showing the image formation by a concave lens when an object is placed beyond twice the focal length of the lens.