Question

Q-5. Answer the following questions.
(1) Name all the colours present in white light, starting from red in proper order.
(2) Name major defects of love of the human eye. How are these defects overcome??
(3) State 4 characteristics of an image formed by a plane mirror.
(4) Describe an experiment to prove that sound cannot travel through vacuum.
(5) What is the range of audible? Vibrations for the normal human ear?
(6) Hello Name 3 major classes of musical instrument and explain how the sound is produced by them.
(7) How is rolling friction caused?
(8) Why is friction called a necessary evil?
(9): name 4 ways by which friction can be reduced between 2 surfaces incontact.
(10)What is the limiting friction? State the laws of limiting friction.
(11) How is pressure related to force?
(12)why does the nose of some people start Bleeding at higher altitudes?
(13)Why does the ink from a fountain pen leak at higher altitudes?
(14)why is a tank made to move over a wide steel belt?
(15)What is the Red Data book?
(16)What steps would you undertake to protect the biodiversity of your area?
(17) What are the consequences of Deforestation.?
(18) How has the use of CNG in motor vehicles reduced pollution in the big cities? Explain.
(19) which zone of flame is used by Goldsmiths to make gold ornaments and why??
(20)Why it is easy to burn a heap of dry grass compared to green grass?​

Answer 1

1) Red, Orange, Yellow, Blue, Indigo, Violet

3) --

• The image is of the same distance as the object is from the mirror
• The image is of the same size of the object
• The image is Virtual
• The image is erect

I know only this much but i hope it helps

Answer 2

Answer:

1. Red, Orange, Yellow, Green, Blue, Indigo and Violet
2. Hypermetropia, Myopia, Cataract

3.The image formed by a plane mirror is always virtual and erect.., The size of the image is equal to that of the object..,The image formed is as far behind the mirror as the object in front of it..,The image is laterally inverted

4.The experiment is done by placing an electrical bell in the bell jar..As the air is pumped out of the sealed bell jar,the sound from the bell jar fades.. However,the sound is not audible to our ears becoz of the vaccum inside the jar..This demonstrates that the sound wave cannot travel through vaccum

5. about 20 to 20,000Hz

The normal hearing frequency range of a healthy person is about 20 to 20,000 Hz..

6.There are three families of musicial instruments- string,wind and percussion..When a string is plucked on an instrument such as guitar,the vibration is passed into the air and you hear a sound..

7. Rolling friction occurs when a wheel,ball or cycinder rolls freely over a surface,as in ball and roller bearings..The main source of friction in rolling appears to be dissipation of energy involved in deformation of the objects.

8.Fricitonal force causes a lot of losses in general upkeep and wear and tear machinery..Hence it is cosidered as a evil..But almost all crucial tasks cannot be carried out without the presence of friction..Hence it is considered as a necessary evi..

9.Polishing the surface.., Using a lubricant..,Using a ball-bearing