Science [5 marks Questions]

i. a. Object is placed between F and 2F of thin converging lens .
b. Object is placed between optical centre and F.
ii. The ray diagrams for real magnified and virtual magnified images are as follows:
Part (a) :


Part (b)

iii. a. There will be no change in focal length of converging lens.
b. Intensity will become one-fourth and brightness of lens will be less .

Light rays that are parallel to the principal axis of a concave mirror converge at a specific point on its principal axis after
reflecting from the mirror. This point is known as the principal focus of the concave mirror
Principal focus (p.f.) is a point on principal axis of a concave mirror where the rays parallel to principal axis meet after reflection
from the mirror.



Additional reading. For convex mirror, principal focus is a point on principal axis of a convex mirror where rays parallel to
principal axis appear to diverge from after reflection from the mirror.

The working together of various organs of human being in a systematic, controlled and efficient way to produce a proper response to various stimuli is known as coordination.
In human beings, the control and coordination is brought about by both nervous system and endocrine system. Nervous system
consists of receptors that receive the stimulus from surrounding environment and send the message received by them to the spinal cord and brain in form of electrical impulses through the sensory nerves.
The motor nerves then transmit the response to the effector. The effectors are mainly the muscles and glands of our body. Thus,
endocrine glands secreting hormones are directly or indirectly controlled by the nervous system. For example, when an emergency stimulus is detected by the nervous system, the stimulus is detected by the nervous system , the stimulus is received and analysed by central nervous system that send message to effectors to provide proper response. At the same time, the sympathetic nervous system activates adrenal gland to release adrenaline that prepares body by increasing heart rate, blood pressure,respiration and dilates pupil etc.
Hence, control and coordination in humans (or animals) depend on two things for transmitting information, i.e. chemical signals
of hormones and nerve impulses.
If they depended only on nerve impulses through nerve cells, only a limited range of tissues would be stimulated. Since, they get
additional chemical signals as well, a large number of tissues are stimulated. This is why animals can show a wide range of
response to stimulus.

The basic requirements for sexual reproduction are the involvement of male and female individuals which will contribute the male
and female gametes respectively. The gametes are haploid that are produced through meiosis which on fertilization produce a zygote and the normal diploid number of chromosomes is restored in offsprings.
The importance of sexual reproduction is as follows:
i. It provides variations in species.
ii. Two individuals are required one male and another female.
iii. Specialized organ called sex organ are involved in this type of reproduction
iv. It promotes diversity of characters in offsprings.
v. It results in recombination of genes thus increase chances of genetic variations.
vi. It plays an important role in origin of new species.