Which of the following are the primary colours of light ?
- A.Yellow, Red and Green
- B.Blue, Red and Green
- C.Violet, Red and Yellow
- D.Indigo, Violet and Green
Correct answer
Explanation
The correct answer is B, Blue, Red and Green. Red, green and blue are the primary colours of light because mixing them in different proportions produces all other colours.
This is additive colour mixing: red and green light give yellow, green and blue give cyan, blue and red give magenta, and all three together give white light. The human retina has three kinds of cone cells, most sensitive to red, green and blue, which is why these three work as primaries. Television, mobile and computer screens make every colour from tiny red, green and blue (RGB) dots.
A is wrong because yellow is a secondary colour of light, made from red and green.
C is wrong because violet and yellow are not primaries; yellow is formed by mixing red and green light.
D is wrong because indigo and violet are spectral colours of white light, not primary colours.
Exam tip: primaries of light are RGB; red, yellow and blue are the painter's primaries for pigments.
Practice Questions
View allWhich one of the following statements about classification of plants is correct?
- A.Thallophytes have well differentiated body design
- B.Funaria is a fungus
- C.All Pteridophytes are Phanerogams
- D.Vascular system is not found among Bryophytes
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Mosses and liverworts have no xylem or phloem, so water moves through them cell to cell. Bryophytes, such as Funaria (a moss) and Marchantia (a liverwort), are called the amphibians of the plant kingdom because they live on land but need water for fertilisation.
Read the full explanation →Which one of the following reactions will give NO (nitric oxide) gas as one of the products?
- A.3Cu + 8HNO3 (dilute) →
- B.Cu + 4HNO3 (conc.) →
- C.4Zn + 10HNO3 (dilute) →
- D.Zn + 4HNO3 (conc.) →
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Copper with dilute nitric acid gives copper nitrate, water and nitric oxide: 3Cu + 8HNO 3 → 3Cu(NO 3 ) 2 + 2NO + 4H 2 O. Nitric acid is a strong oxidising agent, so metals usually do not release hydrogen from it; instead the acid itself is reduced, and…
Read the full explanation →10 g of ice at −10°C is mixed with 10 g of water at 0°C. The amount of heat required to raise the temperature of mixture to 10°C is
- A.400 cal
- B.550 cal
- C.1050 cal
- D.1200 cal
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The heat needed is 50 cal to warm the ice to 0°C, 800 cal to melt it, and 200 cal to warm all 20 g of water to 10°C. Take the specific heat of ice as 0.5 cal/g°C, the latent heat of fusion of ice as 80 cal/g and the…
Read the full explanation →Vinegar is also known as
- A.ethanoic acid
- B.nitric acid
- C.sulphuric acid
- D.tartaric acid
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Vinegar is a dilute solution of ethanoic acid, commonly called acetic acid, in water. Vinegar contains about 5 to 8 per cent ethanoic acid (CH 3 COOH) and is made by the fermentation of sugar or alcohol by acetic acid bacteria.
Read the full explanation →Transformation of meristematic cells into specific permanent tissues occurs by the process of
- A.Cell differentiation.
- B.Cell division.
- C.Cell multiplication.
- D.Cell regeneration.
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Cells made by the meristem lose the ability to divide and take on a fixed shape, size and job, and this change is called differentiation.
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