Physical Science Important Questions

An object is placed 15 cm in front of a concave mirror of focal length 10 cm. Use the mirror formula to find the image distance. State whether the image is real or virtual.

What is magnification? A concave mirror produces an image three times the size of the object. If the object is 20 cm from the mirror, find the image distance and determine whether the image is erect or inverted.

Distinguish between a concave mirror and a convex mirror with respect to the type of images they form. Give one practical use of each.

State Snell's law of refraction. A ray of light passes from air into water. If the angle of incidence is 45° and the refractive index of water is 1.33, find the angle of refraction.

Define total internal reflection. State the two conditions necessary for total internal reflection to occur. Give one real-life application.

An object is placed 30 cm from a convex lens of focal length 10 cm. Using the lens formula, find the image distance and state the nature of the image formed.

Define the power of a lens. A convex lens has a focal length of 25 cm. Calculate its power. If two such lenses are placed in contact, what is the combined power?

Describe myopia (short-sightedness). Explain its cause and state how it is corrected. Draw a ray diagram to show the defect and its correction.

What is meant by the power of accommodation of the human eye? How does this power change with age, and what condition does this lead to in old age?

Three resistors of 4 Ω, 6 Ω, and 12 Ω are connected in parallel across a 12 V battery. Find the equivalent resistance, the total current drawn from the battery, and the current through each resistor.

State Joule's law of heating. A 60 W bulb is used for 5 hours daily. Calculate the electrical energy consumed in one week. Express your answer in kilowatt-hours.

Define electric power. Derive the expression P = I²R from Ohm's law and the definition of power.

State Fleming's left-hand rule. Explain how it is used to determine the direction of force on a current-carrying conductor in a magnetic field.

Explain the principle of electromagnetic induction. State Fleming's right-hand rule and describe one device that works on this principle.

Compare alternating current (AC) and direct current (DC) under the following headings: direction of flow, generation, transmission efficiency, and domestic use.

Balance the following chemical equations: (a) Fe + O₂ → Fe₂O₃ (b) Al + HCl → AlCl₃ + H₂ (c) Ca(OH)₂ + HCl → CaCl₂ + H₂O

Classify the following reactions and give one example of each: combination, decomposition, single displacement, double displacement.

What is oxidation and reduction? Identify the substance oxidised and the substance reduced in the reaction: CuO + H₂ → Cu + H₂O

Explain the pH scale. A solution has a pH of 3. Is it acidic, basic, or neutral? How does the pH change when you add water to an acid?

Name three acid-base indicators and describe the colour change each shows in acidic and basic solutions.

Write the chemical equation for the reaction between sodium hydroxide and hydrochloric acid. What type of reaction is this called? What is the general name for the salt produced?

Write the electronic configuration of the following elements and state their valency: (a) Sodium (Z=11) (b) Chlorine (Z=17) (c) Calcium (Z=20)

Define isotopes and isobars. Give one example of each and explain why isotopes of the same element have identical chemical properties.

Describe how atomic radius changes across a period and down a group in the modern periodic table. Give reasons for the trends observed.

State the modern periodic law. How does it differ from Mendeleev's periodic law? Explain two advantages of the modern periodic table over Mendeleev's table.

Name the functional groups present in: (a) ethanol (b) ethanoic acid (c) formaldehyde. Write the structural formula for each.

What is a homologous series? Give the first three members of the alkane series and state two characteristics that define a homologous series.

Explain how soap acts as a cleaning agent. Define the terms micelle, hydrophilic, and hydrophobic in this context.

Arrange the following metals in order of reactivity (most to least reactive) and explain how you determined the order: Copper, Zinc, Iron, Aluminium.

Describe the process of extraction of iron from its ore in a blast furnace. State the chemical reactions involved at each stage.

Define corrosion. Explain why iron rusts but aluminium does not corrode easily in air. Write the chemical equation for rusting of iron.