diff --git a/in_one_weekend/src/material.zig b/in_one_weekend/src/material.zig
index 33df95e..26b6396 100644
--- a/in_one_weekend/src/material.zig
+++ b/in_one_weekend/src/material.zig
@@ -58,13 +58,21 @@ pub const Dielectric = struct {
         const sin_theta = math.sqrt(1.0 - cos_theta * cos_theta);
 
         const cant_refract = refraction_ratio * sin_theta > 1.0;
-        const direction = if (cant_refract) unit_direction.reflect(hit.normal)
+        const should_reflect = reflectance(cos_theta, refraction_ratio) > rng.float(f32);
+        const direction = if (cant_refract or should_reflect) unit_direction.reflect(hit.normal)
             else unit_direction.refract(hit.normal, refraction_ratio);
         return ScatteredRay{
             .ray = Ray{ .origin = hit.p, .direction = direction},
             .color = attenuation,
         };
     }
+
+    fn reflectance(cosine: f32, ref_idx: f32) f32 {
+        // Use Schlick's approximation for reflectance.
+        var r0 = (1 - ref_idx) / (1 + ref_idx);
+        r0 = r0*r0;
+        return r0 + (1 - r0) * math.pow(f32, 1 - cosine, 5);
+    }
 };
 
 pub const ScatteredRay = struct {