Chapter: Life Sciences
The twinkling of a star is due to the atmospheric
The twinkling of stars is explained by the principle of atmospheric refraction, which occurs when light waves bend as they pass through varying densities in the atmosphere.
As light from a distant star travels through the Earth's atmosphere:
Stars behave as point sources due to their vast distance, enhancing this phenomenon.
Remember: "Twinkle for the refractive kind!" The term "refraction" can help recall that it's the bending of light causing twinkling.
A diagram illustrating layers of the atmosphere with rays of light bending at different layers, depicting the refraction process affecting starlight.
Verified against NCERT Class 9 Science, Chapter on Light.
What is the time gap in occurrence of two successive tides at a given place on the ocean surface ?
The time gap between two successive high or low tides at any given location is influenced by the gravitational pull of the moon and the sun, leading to the phenomenon known as tidal intervals.
The lunar day (the time it takes for the moon to return to the same position relative to the Earth) is about 24 hours and 50 minutes. Since there are two high tides and two low tides during this period:
Option (a): 12 hours - This represents only one tidal interval and does not account for the lunar cycle.
Option (c): 24 hours - This is the solar day calculation, not suitable for tides.
Option (d): 24 hours 52 minutes - This figure overshoots the average tidal influence over lunar cycles.
Remember the lunar cycle's effect: "Lunar pulls lead to tides, twice in a day." This hints at two high and low tides within approximately 13 hours apart.
Illustrate a tidal chart showing high and low tide alternations over a 24-hour period, highlighting the lunar influence and marking the 12-hour 26-minute intervals for clear understanding.
Verified against NCERT Class XII Geography, Chapter on Oceanography and Tides.
Which of the following are the primary colours of light?
The primary colours of light are foundational in the additive colour theory. They combine to create all other colours.
The primary colours of light are:
These colours blend in various proportions to produce other hues:
In everyday life, these colours are evident in screens, lighting, and artistic expressions.
- **Option A**: Yellow, Red, and Green – not primary colours of light.
- **Option C**: Violet, Red, and Yellow – mixes rather than primary.
- **Option D**: Indigo, Violet, and Green – not primary colours of light.
Remember the acronym RGB for Red, Green, and Blue
A diagram depicting the RGB colour model, showing how red, green, and blue light overlap to produce different colours, including secondary colours.
Verified against NCERT Class 9 Science, Chapter on Light.
The amount of air breathed in and out during a normal respiration by human lungs is referred to as
The tidal volume (TV) is the volume of air inhaled or exhaled during a normal breath, typically about 500 mL in adults.
The concept of tidal volume is vital in identifying respiratory health. In normal breathing:
Tidal volume is crucial in assessing lung function and is considered in respiratory therapy and athletic training.
Remember the acronym "TV" to recall Tidal Volume, as it directly relates to typical breath volume during rest.
Consider a diagram depicting the process of normal inhalation and exhalation with labeled tidal volume levels to illustrate the airflow changes in the lungs.
Verified against NCERT Class XII Biology, Chapter on Human Physiology.
Which of the following is/are the applied forcesi n mechanical weathering process?
1. Gravitational force
2. Expansion force
3. Force due to water pressure
Select the answer using the code given below:
Option D is correct. All three forces contribute to mechanical weathering.
Mechanical weathering processes involve physical forces that break down rocks without altering their chemical composition, primarily through gravitational, expansion, and water pressure forces.
Remember G.E.W. (Gravitational, Expansion, Water) to quickly recall the main forces in mechanical weathering.
All applied forces—gravitational, expansion, and water pressure—play crucial roles in mechanical weathering.
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