Gravitational Lensing Dark Matter Quiz: Explore Cosmic Evidence

11th Grade

Reviewed by Ekaterina Yukhnovich

Ekaterina Yukhnovich, PhD |

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Ekaterina V. is a physicist and mathematics expert with a PhD in Physics and Mathematics and extensive experience working with advanced secondary and undergraduate-level content. She specializes in combinatorics, applied mathematics, and scientific writing, with a strong focus on accuracy and academic rigor.

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By Thames

Thames

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| Questions: 20 | Updated: Mar 13, 2026

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1. Weak lensing is especially valuable because it can:

Measure sound speed

Map mass (including dark matter) over large areas

Change star colours

Stop galaxies from forming

Weak lensing maps mass. Weak lensing measures tiny distortions in many background galaxies. Those distortions reveal the gravitational influence of mass, visible or not.

Explanation

Weak lensing maps mass. Weak lensing measures tiny distortions in many background galaxies. Those distortions reveal the gravitational influence of mass, visible or not.

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About This Quiz

Gravitational Lensing Dark Matter Quiz: Explore Cosmic Evidence - Quiz

This assessment delves into gravitational lensing and its implications for dark matter in the cosmos. It evaluates your understanding of key concepts such as light bending, mass distribution, and the evidence supporting dark matter theories. Engaging with this content enhances your grasp of astrophysical phenomena and the universe's structure, making... see moreit highly relevant for learners interested in cosmology and astrophysics. see less

2. What first name or nickname would you like us to use?

You may optionally provide this to label your report, leaderboard, or certificate.

2. Lensing measurements respond to total mass, not just the luminous (visible) matter.

True

False

Gravity depends on total mass-energy. So lensing 'weighs' both stars/gas and dark matter.

Explanation

Gravity depends on total mass-energy. So lensing 'weighs' both stars/gas and dark matter.

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3. In weak lensing, the term 'shear' refers to:

A colour shift

A small stretching/distortion of galaxy shapes

A change in temperature

A change in galaxy mass

Shear is a directional distortion, like slightly squashing a circle into an ellipse. It’s subtle in single galaxies but clear statistically.

Explanation

Shear is a directional distortion, like slightly squashing a circle into an ellipse. It’s subtle in single galaxies but clear statistically.

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4. The main challenge in weak lensing is that galaxies have random intrinsic ______.

Each galaxy has its own shape and orientation. You need many galaxies to average out that randomness.

Explanation

Each galaxy has its own shape and orientation. You need many galaxies to average out that randomness.

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5. Which observation best supports the presence of dark matter using lensing?

Stars appear hotter

Lensing indicates more mass than can be explained by visible matter alone

Galaxies become louder

The speed of light changes

If lensing shows strong gravity where little light is present, it implies unseen mass. This is one of the strongest lines of evidence for dark matter.

Explanation

If lensing shows strong gravity where little light is present, it implies unseen mass. This is one of the strongest lines of evidence for dark matter.

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6. Weak lensing is often used to study the 'cosmic web' of matter.

True

False

Matter forms a web-like distribution on huge scales. Weak lensing helps trace this pattern because it responds to mass.

Explanation

Matter forms a web-like distribution on huge scales. Weak lensing helps trace this pattern because it responds to mass.

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7. 'Convergence' in lensing (qualitatively) is most related to:

Sound focusing

Overall magnification/size change due to mass concentration

Magnetic field direction

Nuclear decay rate

Convergence describes how mass causes rays to converge, increasing magnification. It’s like an overall focusing effect, distinct from shear.

Explanation

Convergence describes how mass causes rays to converge, increasing magnification. It’s like an overall focusing effect, distinct from shear.

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8. A lensing 'mass map' is primarily built from:

The lens’s colour

Measured distortions of many background galaxies

The lens’s temperature

The source’s distance only

Lensing doesn’t measure mass directly with a scale; it infers it from how images are distorted. Many background galaxies provide enough data to reconstruct mass distribution.

Explanation

Lensing doesn’t measure mass directly with a scale; it infers it from how images are distorted. Many background galaxies provide enough data to reconstruct mass distribution.

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9. Two clusters with the same visible brightness could still lens differently if their dark matter distributions differ.

True

False

Lensing depends on total mass distribution, not brightness. Different dark matter halos can produce different shear patterns.

Explanation

Lensing depends on total mass distribution, not brightness. Different dark matter halos can produce different shear patterns.

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10. Which is an example of 'lensing systematics' that scientists must correct for?

Planet seasons

Telescope blurring that changes measured galaxy shapes

Galaxy names

Sound echoes

Instrument effects can mimic or hide tiny distortions. Careful calibration is essential in weak lensing surveys.

Explanation

Instrument effects can mimic or hide tiny distortions. Careful calibration is essential in weak lensing surveys.

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11. Weak lensing usually requires ______ of galaxies, not single objects, to measure reliably.

The signal is small compared with intrinsic shape scatter. Large samples raise the signal-to-noise.

Explanation

The signal is small compared with intrinsic shape scatter. Large samples raise the signal-to-noise.

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12. A major difference between strong and weak lensing is that weak lensing:

Produces many obvious multiple images

Produces small distortions that need statistical analysis

Requires only one background star

Works only in the solar system

Strong lensing is obvious in individual systems. Weak lensing is subtle and needs many galaxies and careful analysis.

Explanation

Strong lensing is obvious in individual systems. Weak lensing is subtle and needs many galaxies and careful analysis.

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13. Weak lensing can be used to estimate how the universe’s structure grows over time.

True

False

By measuring lensing at different distances (look-back times), scientists infer how clumps of matter evolve. This helps test cosmological models.

Explanation

By measuring lensing at different distances (look-back times), scientists infer how clumps of matter evolve. This helps test cosmological models.

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14. If a region shows a strong shear pattern but little visible light, the best interpretation is:

The shear is impossible

There may be significant dark matter there

Light has stopped existing

The speed of light must be variable

Shear traces gravitational influence. A 'mass without light' signal suggests unseen matter.

Explanation

Shear traces gravitational influence. A 'mass without light' signal suggests unseen matter.

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15. Which lensing observations can help map mass?

Galaxy shape distortions (shear)

Magnification trends in background counts

Positions/arcs in strong lensing systems

The lens’s soundtrack

Shear and magnification both carry mass information. Strong lensing arcs/positions also constrain the mass distribution.

Explanation

Shear and magnification both carry mass information. Strong lensing arcs/positions also constrain the mass distribution.

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16. Lensing can distinguish between different mass distributions even if total mass is similar.

True

False

Where mass is located affects distortions and arc shapes. Two lenses with equal mass can lens differently if one is more concentrated or asymmetric.

Explanation

Where mass is located affects distortions and arc shapes. Two lenses with equal mass can lens differently if one is more concentrated or asymmetric.

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17. A 'mass concentration' tends to cause background galaxies to appear:

Randomly noisier only

Preferentially distorted in a pattern around the concentration

All perfectly circular

Always redder

Weak lensing produces coherent distortion patterns correlated with mass. The pattern helps locate and characterize the mass.

Explanation

Weak lensing produces coherent distortion patterns correlated with mass. The pattern helps locate and characterize the mass.

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18. Which statement best explains why lensing is powerful for dark matter studies?

Dark matter emits bright light

Dark matter affects gravity, and lensing measures gravity’s effect on light

Dark matter changes c

Dark matter is magnetic only

Dark matter is hard to see directly because it doesn’t emit light. But it still bends light via gravity, so lensing reveals it.

Explanation

Dark matter is hard to see directly because it doesn’t emit light. But it still bends light via gravity, so lensing reveals it.

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19. Weak lensing surveys need precise shape measurement and careful correction for observational biases.

True

False

The distortions are tiny, so small measurement errors matter. That’s why survey design and calibration are crucial.

Explanation

The distortions are tiny, so small measurement errors matter. That’s why survey design and calibration are crucial.

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20. Grade 11 wrap-up (less obvious): If two lens models predict the same arc positions but different shear patterns farther out, the best conclusion is that:

Both models must be identical everywhere

Arc positions constrain the inner mass well, but the outer mass distribution can still differ

Lensing cannot measure mass

Shear has nothing to do with mass

Strong lensing features mostly constrain the core region of the lens. Weak lensing/shear can probe broader, outer mass structure, so models can differ there.

Explanation

Strong lensing features mostly constrain the core region of the lens. Weak lensing/shear can probe broader, outer mass structure, so models can differ there.

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