Short & Long Question Answers: To Truly Understand a Rainbow | Gul Mohar Class 7: Book Solutions, Summaries & Worksheets PDF Download

Short Question Answers

Q2: What was the Great Plague and how did it affect Newton?
Ans: The Great Plague spread across London and killed thousands of people, forcing many to leave the city. Newton had to leave his college and return to his childhood home, Woolsthorpe Manor, where he used the quiet time for scientific thinking and experiments.

Q3: How did Newton’s purchase of a prism influence his ideas?
Ans: Newton bought a prism from the market, which soon caught his attention at home. While most students relaxed, he began experimenting with it. The prism made him curious about the real nature of light and colour, inspiring discoveries that changed science.

Q4: What did scientists like Aristotle and Robert Hooke believe about white light?
Ans: Aristotle and Hooke believed that white light was simple and solid, and colour came from mixing white with black. Hooke even created a colour scale, thinking that darkness mixed with light produced various shades, but Newton did not agree with these views.

Q5: How did Newton prove earlier scientists wrong?
Ans: Newton noticed that a white page with black writing did not appear coloured, but only grey. This made him doubt Aristotle and Hooke’s ideas. His careful experiments with prisms showed that colours were not mixtures of light and darkness but already present in white light.

Q6: What did Newton discover when he placed the prism far from the window?
Ans: When Newton positioned the prism at a distance, he saw the sunlight spread into different colours forming a spectrum. He realized that white light was not one single thing but contained many colours, each bending differently when passing through the prism.

Q7: What was Newton’s theory about colours and wavelengths?
Ans: Newton concluded that each colour was made of light waves with different wavelengths. Shorter wavelengths like violet bent more, while longer ones like red bent less. This explained why a prism separated white light into different colours in a visible spectrum.

Q8: What did Newton’s experiment with pure green light prove?
Ans: Newton allowed only green light to pass through a slit and then directed it into another prism. The green light stayed green, showing the prism did not add colour. This proved that colours already existed in white light and were simply separated.

Q9: How did Newton become the first to truly understand a rainbow?
Ans: By proving that white light is made of many colours and that prisms separate them by bending different wavelengths, Newton realized this was how rainbows form in nature. His discovery explained rainbows scientifically, making him the first to truly understand them.

Q10: Why was Newton’s discovery about light and colours significant?
Ans: Newton’s discovery was significant as it showed that natural phenomena were governed by scientific principles. It also marked a new stage in his life, making him confident that the natural world could be explained through experiments, not just old beliefs.

Long Question Answers

Q2: What did Newton observe in his experiment with the prism and sunlight?
Ans: Newton set up his prism twenty-two feet away from the window and allowed a narrow beam of sunlight to pass through it. He observed that the white beam spread into several colours, which he called a spectrum. The colours were red, orange, yellow, green, blue, indigo, and violet. From this, he concluded that white light was not simple but contained all other colours. His experiment changed the long-standing belief that colour came from mixing light with darkness.

Q3: Explain Newton’s theory about wavelengths and bending of light.
Ans: Newton’s theory was that each colour was made of light waves, and each wave bent differently when it passed through a refracting object like a prism. Shorter wavelengths, such as violet, bent more sharply, while longer wavelengths, like red, bent less. This bending separated white light into its component colours, forming the visible spectrum. Newton’s clear explanation helped people understand that colours already existed in white light and were not created by the prism, but only spread apart by it.

Q4: Describe Newton’s crucial experiment with pure green light.
Ans: To prove that the prism was not creating colours, Newton performed a crucial experiment. He used a screen with a slit to allow only green light from the spectrum to pass through. Then he directed this green light into a second prism. If the prism itself created colours, the green would have changed into another shade. However, the light remained green. This proved that prisms only separate colours already present in white light and do not add new ones.

Q5: Why was Newton’s discovery about light considered groundbreaking?
Ans: Newton’s discovery was groundbreaking because it replaced old beliefs about light with clear scientific proof. He showed that white light contains all colours, each with its own wavelength, and prisms only separate them. This was the first time anyone had truly explained how a rainbow forms. His experiments proved that nature followed scientific laws, which could be tested and explained. This discovery not only changed the study of light but also established Newton as one of the greatest scientists in history.