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Diagrams are some of the most predictable marks in Class 10 science, and also some of the most often lost, through missing labels, wrong arrows or a drawing from a chapter that is not in this year's exam. This post lists the diagrams worth practising for 2026-27, flags what has moved out of the year-end exam, works through a lens question from the sample paper, and gives a short routine.
What has changed for 2026-27?
The CBSE Class 10 Science curriculum for 2026-27 keeps five units and an 80-mark theory paper. It says some topics "will be assessed only formatively", that is, in school and not in the year-end exam:
Periodic Classification of Elements
Evolution
Motor, Electromagnetic Induction and Electric Generator
So the electric motor and generator diagrams are not the priority for the board paper this year. The curriculum also excludes the colour of the sun at sunrise and sunset, and says information in NCERT boxes will not be assessed. Check the curriculum for your exam year, because these lists change.
How many marks can one diagram carry?
In the 2026-27 sample paper, Question 39 offers a choice: draw how a corrective lens helps a myopic eye see distant objects, or draw a labelled diagram of white light splitting through a glass prism. The marking scheme gives that diagram 2 of the question's 5 marks.
Which diagrams should you practise?
From the current NCERT Class 10 Science chapters:
Open and closed stomata (Figure 5.3)
Human alimentary canal (Figure 5.6)
Human respiratory system (Figure 5.9)
Sectional view of the human heart (Figure 5.10)
Human excretory system and the structure of a nephron (Figures 5.13 and 5.14)
Structure of a neuron (Figure 6.1)
Reflex arc (Figure 6.2)
Human brain (Figure 6.3)
Binary fission in Amoeba and budding in Hydra (Figures 7.1 and 7.4), which also appear in the practical list
Longitudinal section of a flower and germination of pollen on the stigma (Figures 7.7 and 7.8)
Human male and female reproductive systems (Figures 7.10 and 7.11)
Light and The Human Eye and the Colourful World
Ray diagrams for concave and convex mirrors and lenses
Myopia and its correction, hypermetropia and its correction (Figures 10.2 and 10.3)
Refraction through a triangular prism and dispersion of white light (Figures 10.4 and 10.5)
Magnetic Effects of Electric Current
Field lines around a bar magnet, a straight conductor and a solenoid
Worked example: a lens question with a diagram
Question 35 of the sample paper: a concave lens forms an image one-third the size of the object, which is 24 cm in front of the lens. Find the image distance and focal length.
Use the sign convention: u = −24 cm. For a lens, magnification m = v/u, and a concave lens gives an upright, smaller image, so m = +1/3.
v = m × u = (1/3) × (−24) = −8 cm. The image is 8 cm from the lens, on the same side as the object.
Lens formula: 1/f = 1/v − 1/u = 1/(−8) − 1/(−24) = −3/24 + 1/24 = −2/24 = −1/12.
So f = −12 cm. The negative sign confirms a diverging lens.
These match the marking scheme. When you draw it, show one ray parallel to the axis that diverges as if from the focus on the object side, one ray through the optical centre undeviated, and the virtual image where the backward extensions meet, with arrows on every ray.
Which mistakes cost diagram marks?
Missing arrows on light rays or blood flow.
Solid lines for virtual rays. Use dotted lines for extensions.
Unlabelled vessels. In the heart and nephron, label the blood vessels as well as the chambers or parts.
Mixing up the eye defects. Myopia uses a concave lens; hypermetropia uses a convex lens.
Practising a formative-only topic first while board diagrams are weak.
A practice routine
Make a list of the diagrams above and tick each one off.
Draw from memory, then compare with NCERT. Correct labels in a different colour.
Two diagrams a day, five minutes each, one biology and one physics.
Weekly, a timed mixed set of three diagram questions.
For ray diagrams that will not settle in your head, the Fermi Simulation Lab has interactive simulations for ideas easier to see than read, so you can move the object and watch the image change before drawing it.
Our posts on life processes, defects of the human eye and the Class 10 science paper go deeper.
Tonight, draw the human heart and the prism dispersion diagram from memory, then check every label against NCERT.
