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Practice Class 10 Science MCQs based on NCERT concepts covering resistance, homologous organs, accommodation of the eye, trophic levels, and power of a lens. Get answers with clear exam-focused explanations.
Do You Know
Chapter Information
Subject: Science
Class: 10
Question Type: Multiple Choice Questions (MCQs)
Difficulty Level: Moderate
Based On: NCERT-aligned concepts
Introduction
This Class 10 Science MCQ practice set covers important concepts from Electricity, Heredity and Evolution, Human Eye and Colourful World, Our Environment, and Light. These questions are useful for strengthening conceptual understanding and preparing for school and board examinations.
What You Will Learn
✔ Resistance and factors affecting resistance
✔ Homologous organs and evolutionary relationships
✔ Accommodation of the human eye
✔ Trophic levels in an ecosystem
✔ Power of a lens and its unit
Why This Topic Is Important
These concepts are frequently used in Class 10 Science examinations. Understanding the underlying ideas helps students answer both direct MCQs and concept-based questions more confidently.
Exam Relevance
These questions can be useful for:
✔ CBSE and NCERT-based examinations
✔ School tests
✔ Unit tests
✔ Half-yearly examinations
✔ Annual examinations
✔ Science revision and MCQ practice
Q1. Resistance of a conductor is inversely proportional to its:
A) Length
B) Temperature
C) Area of cross-section
D) Material
Answer:
Area of cross-section
Concept / Exam Explanation
The resistance of a uniform conductor is given by:
$$R=\rho\frac{L}{A}$$
where:
- $$R$$ = resistance
- $$\rho$$ = resistivity
- $$L$$ = length of conductor
- $$A$$ = area of cross-section
From the formula:
$$R\propto\frac{1}{A}$$
Therefore, when the area of cross-section increases, resistance decreases, provided other factors remain unchanged.
Exam Tip
Remember:
$$R\propto L$$
and
$$R\propto\frac{1}{A}$$
Q2. Which of the following is an example of a homologous organ?
A) Our teeth and an elephant’s tusks
B) Our arm and a dog’s foreleg
C) Potato and runners of grass
D) All of the above
Answer:
All of the above
Concept / Exam Explanation
Homologous organs have a common basic structural origin but may perform different functions.
Examples include:
- Human arm and dog’s foreleg
- Human teeth and elephant tusks
- Potato and grass runners are modified stem structures
These examples help demonstrate similarities in basic structure or origin despite differences in their functions.
Exam Tip
Homologous organs are important evidence for studying evolution and common ancestry.
Q3. The change in focal length of an eye lens is caused by the action of:
A) Iris
B) Pupil
C) Ciliary muscles
D) Retina
Answer:
Ciliary muscles
Concept / Exam Explanation
The ciliary muscles control the shape of the eye lens.
When these muscles change the curvature of the lens, the focal length changes. This allows the eye to focus clearly on objects at different distances.
This ability of the eye to adjust its focal length is called accommodation.
Exam Tip
Remember:
Ciliary muscles → Change shape of lens → Change focal length → Accommodation
Q4. In an ecosystem, herbivores represent which trophic level?
A) Third
B) First
C) Fourth
D) Second
Answer:
Second
Concept / Exam Explanation
The trophic levels generally begin with producers:
First trophic level → Producers
Second trophic level → Primary consumers
Herbivores feed directly on plants, so they are primary consumers and occupy the second trophic level.
Example:
$$\text{Grass}\rightarrow\text{Grasshopper}\rightarrow\text{Frog}\rightarrow\text{Snake}$$
Here, grass is the producer and the grasshopper is the primary consumer.
Exam Tip
Remember:
Producers = 1st trophic level
Herbivores = 2nd trophic level
Primary carnivores = 3rd trophic level
Q5. What is the unit of power of a lens?
A) Watt
B) Joule
C) Meter
D) Dioptre
Answer:
Dioptre
Concept / Exam Explanation
The power of a lens is related to its focal length:
$$P=\frac{1}{f}$$
where $$f$$ is the focal length measured in metres.
The SI-derived unit commonly used for lens power is dioptre (D).
For example, if:
$$f=0.5,m$$
then:
$$P=\frac{1}{0.5}=+2D$$
Exam Tip
A convex lens generally has positive power, while a concave lens has negative power.
The ability of a lens to bend (converge or diverge) light rays is referred to as its power or capacity.
- Definition: The power of a lens is equal to the inverse of its focal length ($f$).
- Formula:
$$P = \frac{1}{f \text{ (in meters)}}$$ - Unit: Its SI unit is the Dioptre, which is denoted by the symbol ‘D’.
- If the focal length of a lens is $1$ meter, its power will be $1 \text{ D}$.
Key Points:
- Convex Lens: Its power is always positive (+).
- Concave Lens: Its power is always negative (-).
- Other Options:
- Meter: The unit of distance.
- Watt: The unit of power (electrical or mechanical).
- Joule: The unit of energy or work.
Important Formulas & Concepts
1. Resistance
$$R=\rho\frac{L}{A}$$
2. Resistance and Length
$$R\propto L$$
3. Resistance and Area
$$R\propto\frac{1}{A}$$
4. Power of a Lens
$$P=\frac{1}{f}$$
where $$f$$ is measured in metres.
5. Trophic Levels
Producers → Primary Consumers → Secondary Consumers → Higher Consumers
6. Accommodation of Eye
Ciliary muscles change the curvature of the lens, which changes its focal length.
Related Practice Questions
- What happens to resistance when the cross-sectional area of a conductor is increased?
- What is the relationship between focal length and power of a lens?
- Why are herbivores called primary consumers?
- What is meant by homologous organs?
- Which muscles help the eye focus on objects at different distances?
Mini Quiz Challenge
1. If the focal length of a lens is 2 m, what is its power?
A) $$0.5D$$
B) $$2D$$
C) $$4D$$
D) $$-2D$$
Answer: $$0.5D$$
2. Which trophic level is occupied by producers?
A) First
B) Second
C) Third
D) Fourth
Answer: First
3. Which factor is inversely related to resistance?
A) Length
B) Area of cross-section
C) Resistivity
D) Current
Answer: Area of cross-section
Exam Tips
✔ Learn the resistance formula and understand the relationship between $$R$$, $$L$$ and $$A$$.
✔ Remember that ciliary muscles are responsible for accommodation of the eye.
✔ Herbivores are primary consumers and occupy the second trophic level.
✔ The power of a lens is measured in dioptres.
✔ Homologous organs provide evidence of evolutionary relationships.
Quick Revision Notes
✔ $$R=\rho\frac{L}{A}$$
✔ Resistance increases with the length of a conductor.
✔ Resistance decreases when the cross-sectional area increases.
✔ Ciliary muscles change the focal length of the eye lens.
✔ Herbivores occupy the second trophic level.
✔ Lens power is measured in dioptre.
✔ Homologous organs have a common basic structural origin.
Common Mistakes Students Make
❌ Confusing the relationship between resistance and area.
❌ Choosing the iris instead of ciliary muscles for accommodation.
❌ Considering herbivores as producers.
❌ Confusing dioptre with metre.
❌ Assuming homologous organs must perform the same function.
Key Takeaways
- Resistance depends on the length, cross-sectional area, and resistivity of a conductor.
- Ciliary muscles help the human eye adjust its focus.
- Herbivores are primary consumers at the second trophic level.
- Lens power is measured in dioptres.
- Homologous structures help explain evolutionary relationships.
FAQs
1. What is the formula for resistance?
$$R=\rho\frac{L}{A}$$
2. Which muscles change the focal length of the eye lens?
Ciliary muscles.
3. Which trophic level contains herbivores?
Second trophic level.
4. What is the unit of lens power?
Dioptre (D).
5. What are homologous organs?
Homologous organs are structures that have a similar basic structural origin but may perform different functions.
Conclusion
This Class 10 Science MCQ practice set covers important concepts from electricity, evolution, the human eye, ecosystems, and light. Understanding the concepts behind each answer is more useful than simply memorising the correct options. Regular practice with NCERT-aligned MCQs can help students improve conceptual clarity and examination readiness.
NCERT Reference
Reference: NCERT Class 10 Science textbook and the concepts prescribed in the NCERT-based Class 10 Science syllabus.
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