CBSE ADDA

Gist of Lesson for Quick Revision (By JSUNIL) 1. An eye is the most important organ of the human body. It is associated with vision and acts as a vital optical instrument. 2. An eye is spherical in shape of about 2.3 cm diameter and is covered externally by a hard thick and opaque layer called Sclerotica. The outermost layer of the eye is sclerotic that  protects  and holds the eye. 3. Cornea is transparent part bulging out of eye and allows the light to enter in the eye. Cornea is also known as the window or aperture of the eye. 4. Iris is a circular diaphragm having a hole in its centre .this hole is called pupil 5. Iris has muscles and coloured pigments that provide different colour y eyes 6. Iris controls the amount of light entering the eye through the pupil. 7. The pupil becomes small when bright light falls on the eye. However, it becomes wide when there is dim light. 8. The eye lens is a crystalline convex lens made up of transparent and flexible tissu

English Language    PSA ENGLISH     (Questions 1 to 8) Read the following passage carefully and select the most suitable option from  each list according to the corresponding  number in the passage The Indian Peafowl, alternatively(1) known as the Blue Peafowl, is the national bird of India.  The male is called a peecok(2) and has  feathers which are made up of a range(3) of beautiful colours.  The female is  called a peahen.   The majority(4) of the female’s feathers are a plain (5)brown colour. These birds usually  live in sparsely  populated areas such as forests and don’t fly very often.  They eat berries, seeds and  sometimes snakes or small animals. Q 1.  Which of the following could replace ‘alternatively’ as  used  in the passage above? 1) and 2) also 3) then 4) never Q 2.    Which of the following is the correct spelling of ‘peecok’? 1) peacok 2) peacock 3) peecock 4) peakock Q 3.   Which of the following could replace ‘a range of’ as used in the

1 Mark Questions Q1. Which sound has a higher pitch, guitar or car horn? Q2. Name three animals which can hear ultrasonic vibrations. Q3. How are the wavelength and frequency of a sound related to its speed? Q4. Why sound wave is called a longitudinal wave? Q5. Frequency of a source of sound is 100 Hz. How many times does it vibrate in a minute? Q6. What is an echo? Q7.What do waves transport - matter or energy? Q8. What is a wave? Q9. Which characteristics of the sound help us to identify a person by his voice if he is sitting in a dark room? Q10. If the amplitude of a wave is doubled, what will be the effect on its loudness? 2 Marks Questions Q11. Which wave property determines a) loudness, b) Pitch? Q12. Why are the ceilings of concert halls curved? Q13. How is ultrasound used for cleaning? Q14. Sound is produced due to a vibratory motion, then why a vibrating pendulum does not produce sound? Q15. A sound produces 20 crests and 20 troughs in 0.4 sec. Find the frequenc

Two marks questions  1. Explain how echoes are used by bats to judge the distance of an obstacle? 2. State the special properties of ultrasound that make it useful to us .In general, how these properties are utilized. 3. Why is soft furnishing avoided in concert halls? 4. Draw a diagram depicting low pitched sound and high pitched sound and write main difference between the two? 5. Distinguish between longitudinal and transverse waves. Give one example each. 6. An explosion takes place at the moon. After what time would it be heard at the earth? Three marks questions 7. Two sources A and B vibrate with the same amplitude. They produce sounds of frequencies 1 kHz and 30 kHz respectively. Which of the two waves will have greater power? 8. Find the time period of the source of a sound wave whose frequency is 400Hz. 9. A sound wave travels at a speed of 340m/s. If its wavelength is 2 cm, what is the frequency of the wave? Will it be in the audible range? 10.